University of California
College of Agriculture
Agricultural Experiment Station
Berkeley, California
Estimating Production of Natural Raisins in California
by Use of List Sampling
by
George M. Kuznets and George Harvey
August 19$2
Contribution from the
Giannini Foundation of Agricultural Economics
Mimeographed Report No. 13&
LIBRARY
university of california
Davis
•
Estimating Production of Natural Raisins in California
by Use of List Sampling*
by
George M. Kuznetsl/and George Harvey^/
During 19U9, 1950, and 1951, the California Crop and Livestock Reporting
Service, a cooperative office of the California State Department of Agriculture
and the Bureau of Agricultural Economics, U. S. Department of Agriculture, pre-
pared and published special estimates of production of raisins in California.
These estimates were based on information provided by specially designed samples
drawn from a listing of raisin-type grape units located in the major producing
counties of the state. Table 1 provides in summary form a schedule of the ex-
perimental surveys during the three seasons. It will be noted that four surveys
were carried out each season, namely, a preharvest survey, two surveys during
the harvesting period (hereafter referred to as within-season surveys) one week
apart, and a final survey.^/ In each of the preharvest surveys, the operators
of sample units were interviewed by specially hired and trained enumerators,
who had a background of experience in the local grape industry. The final sur-
veys were carried out by mail with personal interview follow-up of all nonre-
spondents. In 19h9 and 1950, the within-season surveys were by mail only and in
1951 by interview of one-half of the total sample. The schedules employed in
the 1951 surveys are shown in the Appendix. In addition to raisin production
by main varieties, information was obtained from operators on bearing acreage
in sample units and acreage harvested for production of raisins. In 195lj in-
formation was also obtained prior to harvest on acreage to be harvested for
* The activities discussed herein were conducted under the general direction
of G. A. Scott, State Statistician in charge of the Federal-State Crop and
Livestock Reporting Service in California.
1/ Professor of Agricultural Economics, Economist in the Experiment Station
and on the Giannini Foundation, University of California.
2/ Agricultural Statistician, Bureau of Agricultural Economics, Sacramento.
3/ The following persons supervised the field work for these surveys: 19U9,
Irwin Rust, Extension Service, University of Hawaii; 1950, James H. Swedberg,
Bureau of Agricultural Economics, Sacramento,- 1951, Robert D. Parr, Bureau of
Agricultural Economics, Sacramento.
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2.
TABLE 1
Schedule of Raisin Production Surveys,
California 19U9, 1950, and 1951
Preharvest
survey
First within-
season survey
Second within-
season survey
Final
survey
Field work
Reference^
Closing date
Report date
Field work
Referenced/
Closing date
Report date
Field work
Reference^/
Closing date
Report date
August 5-31
Not issued
August 9-23
MM
August 23
Not issued
August 21-25
August 25
August 29
19JU9 Season
(four- county sample)
September is/
September 5
September 12
September 13
September
September 12
September 19
September 20
1950 Season
(seven- county sample)
August 283^
August 31
September k
September 6
September
September 7
September 11
September 12
1951 Season
(seven-county sample)
September b-5
September k
September 5
September 7
September 11-12
September 11
September 12
September lU
September 23^
October 11
November 3
September 2
October 13
October 19
October 2
October 6
October 10
-62/
2/ Mailing date.
]>/ Date to which observations pertained.
SJ Interview follcw-upj mailing date one week earlier
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3.
raisins and expected total production of raisin grapes and, in the final survey,
on tons of raisin- type grapes harvested for all uses. Funds for this work were
made available jointly by the State Department of Agriculture and the Production
and Marketing Administration under the Research and Marketing Act of 19U6. Mem-
bers of the staff of the Giannini Foundation of the University of California
participated in the planning of these studies, the design of samples, and the
analysis of data collected in the surveys.
The purpose of this report is to provide a description and appraisal of the
procedures employed, with emphasis on the 1951 surveys. Particularly for de-
scriptive material, this report has drawn freely on a memorandum regarding the
several RMA projects on methods of estimating California raisin and grape crops
prepared for administrative use in May, 1951.
Background Information
Of the total production of raisins in California, including both natural
and bleached, over 90 per cent is made from Thompson Seedless variety grapes
and most of the remainder from Muscat, Black Corinth (Zante currant), and
Sultana varieties. In 1951, the bearing acreage of raisin grape varieties in
California was 230,379 acres, of which the Thompson Seedless variety accounted
for 187,1*71* or 8l.it per cent of the total. The other two major varieties,
Muscat and Sultana, accounted only for 36,360 (l5.8 per cent) and h,0k3 (1.8
per cent) bearing acres, respectively. The remainder of the bearing acreage
in 1951, 2,502 acres, included 2,UlU acres of Zante currant. The seven counties
of Fresno, Kern, Kings, Madera, Merced, Stanislaus, and Tulare, in which all
but a few tons of the raisin crop is produced, account for 9l*.l per cent of the
total, and Fresno County alone for 57.0 per cent.
Slightly under 60 per cent of total fresh weight of raisin grapes sold
during the five-year period, I9I46-I95Q, was made into raisins. The other major
outlet for raisin grapes is wine, brandy, or juice. This outlet accounted for
almost 30 per cent of all sales during this period. Of greater relevance to
the problem of efficient estimation of raisin production is the marked year-
to-year variation in utilization of raisin grapes. During the years 19U6, 19U7,
and 19U8, total sales of raisin grapes varied only slightly. However, in 19U6
raisins accounted for hi per cent of total use; in ±9h7 this percentage jumped
to 72; and in 19U8 it dropped to 55. The possibility of abrupt shifts in uti-
lization apart from annual variation in the yield of raisin grapes complicates
the problem of designing an efficient sample for the estimation of raisin pro-
duction.
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Grapes for natural raisins are harvested from late August to late September,
Bunches are removed from the vine and placed on paper or wooden drying trays
(2* x 3') which are laid between vine rows. The average fresh weight of grapes
laid on the drying trays is about 22 pounds. The grapes are left in the sun to
dry for a few weeks, losing about 75 per cent in weight. After rolling or
stacking trays, raisins are placed in sweatboxes or field boxes and left a short
time in the boxes to cure. Following this, raisins may be stored for an in-
definite period of time on the farm or delivered immediately to a handler for
cleaning, sorting, and packing. In 1950, about 1*0 per cent of the natural crop
was delivered by November 1 } 60 per cent by December 1, 71 per cent by January 1,
1951, and 93 per cent by March 1, 1951. Deliveries of the 1951 natural crop
apparently were somewhat earlier, with about 38 per cent delivered by November 1,
7U per cent by December 1, 88 per cent by January 1, 1952, and about 96 per cent
by March 1, 1952.
In addition to the sun-dried or natural raisins, other raisin types which
require much less drying time are made by dipping the grapes in a caustic solu-
tion to break the skin slightly, and then drying them in the open or artificially
by the use of dehydrators. The types most commonly made in California are Golden
Bleached, Sulfur Bleached, and Soda-Dipped raisins, and these together, from 19U6
to 1950, amounted to about 8 per cent of all raisins made. All bleached types of
raisins are made in dry yards or at dehydrators rather than in the field, often
under contract with the buyer. If a raisin grape crop is sold fresh, growers are
paid on fresh ton weight and may or may not know whether their crop will be de-
hydrated. The season for the production of Golden Bleached (artificially de-
hydrated) raisins, the principal bleached type made, may run well into October.
Forecasts and estimates of total production of raisin-type grapes are made
by the Federal-State Crop Reporting Service monthly beginning with July 1, termi-
nating with the Fruit and Nut Crop Annual Summary in December. An estimate of
the seasonal production of raisins based on industry opinion and a preliminary
crop disposition check is first published in the Department's December Annual
Crop Summary and is subject to revision the following June. For the years 1935
to 19U9, the error in this preliminary estimate has ranged from 0.6 to 13.3 per
cent and in 8 of the 15 years it was greater than 5 per cent. The revised esti-
mate is based on available check data which are considered substantially complete.
The Dried Fruit Association of California (D.F.A.C.) makes an estimate of raisin
production which is published in the spring of the year following harvest at a
time when most of the crop has been received by handlers. This estimate is also
subject to revision one year later.
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5.
Sample Design
For all surveys during the three seasons, 19h9, 1950, and 1951 > estimates
were based on information provided by a sample of units drawn in a random-strati-
fied manner from a listing of all raisin grape units. Such a listing was avail-
able from records accumulated in the Crop Reporting Service periodic enumerative
surveys of all fruit acreage by varieties in the state. A vineyard unit is con-
sidered in these records as a block of grapes consisting of one-tenth or more
acres of a single variety. Usually, a unit will contain more than one variety
of grapes. An individual may operate several units, and a single vineyard or
farm may consist of more than one unit, although the single unit vineyard is most
common. Stratification was by county and by bearing acreage of all raisin grape
varieties in unit. Sampling units were allotted by strata for the 19^9 prehar-
vest survey on the basis of total number of units in stratum and the unit standard
deviation of stratum bearing acreage. For later surveys, allocation was made in
proportion to size of stratum and the sample standard deviation of stratum unit
production of raisins. The project was on a trial basis in X9k9 with sampling re-
stricted to the four major producing counties of Fresno, Kings, Madera, and Tulare.
Estimates of raisins made in other producing counties were obtained from members
of the industry. This was not satisfactory from a research standpoint and in
1950 and 1951, units located in Kern, Merced, and Stanislaus counties were added
to the sample, thus providing in the latter two seasons a complete coverage of the
producing areas of sun-dried raisins made from the varieties samples — Thompson
Seedless, Muscat, and Sultana.
The estimates and their (estimated) standard errors shown in Table h for 1950
and 195lj based on the 1951 survey data, were computed with reference to four broad
acreage strata, as shown in the tabulation below, disregarding county breakdowns.
Reference Strata, 1951 Surveys
Number of
Bearing acres
units in
Number
of
Strata
in units
surveyed counties
units in
sample
N h
nh
I
Below k0
10,067
578
II
1*0-99.9
780
liiO
III
100-399.9
161
60
IV
U00 and over
8
J3
Total
11,016
786
n^ 1 iC9Q sJLom.so
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-anrisiq ©rid - *tol eisita yd Be^oils s-isw atinu 3nxIq.tiB2 .tisw ni aaidsiisv
rahnsda titty srid bne flH/iaiia ni silnt; lo todmi/n Isiotf lo eiaad 9/W no ysnna taev
ni ©bBin as* noxixooXIs ^sysvxya 19+sI la's ;9gs9ioB gniiced muiBUe lo neiixivec
1 elds
yeviua
s-iebia
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319 lO
in rrnfi'i
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ni bnfi dnxoqbnsde rtetBeas? c moil yiotfoslaiisa v+on aew siriT .ytrd-airbnr 9di 1c
bebbs e^9w 39ltocoo ansisxnBid bnB t b9oi9M ,ni93 nx b9*Booi scfino ,I??i bxtfi 0591
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noaqreoilT — asiqmse e©i*^i*t»v arfi moil ebsra an/sxBi b9iib-nx»a lo 3£9*ib gnxo^botq
.BtifiiluS, bna .Jcoa^ ,EE9lbee8
?X iol il 9ldsT ni nworia 310119 biBbnsd'a (bejfaniics) ti^Ai bna seitsmiiaa ariT
riiiw b?-fucpoo 9i9vr t Bieb y9viua X?9X pfii no b©p.6d t X5^X bns
rbie^eisxb r woX&d noiJsludzi erii ni iiwria as t sieii3 9S££*iog
l£9ic \fir
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aai.lnjoo bovDvnaa
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•
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6.
The effective stratification comprised many more strata. Not only were units
drawn from size strata of every county included in the survey, but the size strata
were less broad. Within reference Strata I and II, sample units were drawn in a
systematic random manner from size classes of 10 acres and, within Stratum III,
largely from 2$-acre classes (see Table 2). Standard errors computed on the basis
of reference strata would, therefore, tend to overestimate somewhat the sampling
variability of estimates. It should be noted that Stratum IV, consisting of only
8 units, was enumerated. Stratum III was enumerated in the 1950 surveys. In 1951
all of the units of this stratum were contacted for the final survey. It will be
noted from the various entries in Table h, which show for several items, estimates
and their estimated standard errors separately for sampling and enumeration of
Stratum III, that the enumeration of this stratum (which required the addition of
some 100 units to the sample) had neither changed significantly the magnitudes of
the estimates for 1951, nor materially decreased the (estimated) standard errors.
The data shown in Table 7 for the wi thin-season surveys are based on the finer
size stratification as given in Table 2.
Several types of estimates of population totals are shown in Table U:
1. Linear (stratified) . This estimate is of the form
R n,
(1) T. - 2 N, (ETJ, ,/n, )
L , h . hr h
h x
in which X hi is the value of some item for the ith unit in the sample drawn from
stratum h, N h is the total number of units, n h is the number of units in the
sample drawn from stratum h, and R, the number of strata. The variance of T^
is easily shown to be
' w A - 1 - V/SA - u
L h
in which is the population variance in stratum h. An unbiased estimate of
o-j is given by
L h
with s, defined as
h
m -J = 2 h (x hi - r.) Z /\ - i)
i
The estimated standard errors of the linear estimates shown in Table h were cal-
culated using expression (3).
eSinii stow yino ioW .b*s-i.13 ^toffl vnam basrsqmoo noiieoXlXJaite avxioalle 9dT
scfaicN asia ad* dwd ^yftvtua pri.* nx bsbulocfi •fttaooo viava 10. stfaitfe asxs csoil nwxb
s nr nwBifc siaw adxntr alqmaa t II bna I b&bi& aonaialsi ninJxW .bsoid 33 9X trt0&
till aiuJsi^a nidcfiw ,bns aaios 01 lo easaalo esia moil lannara arofcwn 0 .c;J aerate \a
aiaed adj. M bsiuqaoo- siotip M«bc8*8 ,(S aldsT aaa) eac-aaXo eioa-5S moil yXaaial
snxlqsiee MM Jsdwamoa e.t£ntxdr.9X9vo bnai ,9iol9isd.t <bXi/ow aiKiis aonaiel*-! lo
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£&tl nl .ayov^fra 0<K!X ©rii ni b^siarauna aaw III miniiS, .baJs'ianu/na yaw ,3Cfrxru/ 8
ad LIS* il ,^avioe isni'l aritf iol betfoaJiro aiaw rauiaiXa eidj lo sikms lo lis
a «?Jf:-!n itep ipgnji Xsiavee iol worfa rfoirfw <ji aldaT ni a?xi.tae euoxuv 9riJ- moil barfon
lo ttoitetmum bns ^nii'tpnae 10I YXaAair.craB aione bisbnfiia baXxmiJaa liadj fma
lo noxJ/bba adX baixi/pei rioittw) iwcfaiiJa Bhit lo fto/Jaxamunf' add- isdi ,111 nuj.tai.J2
lo aabttfinv^ 9di ^&tas ailing la banned") nadcf-ian bad (aXqmsa- add oJ etinu OCX amoe
. 210119 biabnaJs (bajajridss} ariJ baasoioeb viiaxiadsm ton t I<Ri iol - j .arf-Bi7<ite9 eriJ
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.S sldal nx 097X3 sb noxjJaoilXtffiide asie
:ii oldaT nx rworte aie Bis-JoJ noXJsXyqoq lo as^ranx^ao lo secret XbipvoC
miol gdtf lo ex oJata/dre &xd? . (bailf JsxJ:;) ifi snXJ *l
■
moil nwstb alqmsa arij nl &lnv ciii arid iol maJi amos lo suL&y 9ri^ ai h ,X dpxriw ni
anj nx aixfu; lo ladmun arirf ax ^n <3^xrur lo lad-wn isJ-oJ sd& al rf H ,d nuj^Bi^a
rT lo sonsxiev ariT .ajs Kta lo ladmon sd^ ,H bns .ri mx/Jai^a moil iwetb ali.ur'jSB
(x - /VM^ - rf ; 0 f ,o;:« S - Jo (s)
,ri mixla^a n± soncxiav noxdcluqoq 9ri4 8X ^0 doj
•?d H9VX3 ai
d^VW 1 * d K 'ri K S * T 3 (€)
aa banxlab ' e
it - v.- - ifl x; 5 •- f W
ipjeo-xtap laaniX adtf lo aioiif biabnij^a bevtscXit
TABLE 2
Frequency Distribution of Raisin Grape Units by-
Bearing Acreage
Seven Counties Surveyed— 19^0
Number of
Per cent
Number of
units in
of
units in
count es
bearing
sample
Bearing acreage
surveyed
acre age
0.1- 9.9
3,620
9.1
10- 19.9
U,02U
27.0
20- 29.9
1,101
1U.9
30- 39.9
1,012
15.9
578
Reference stratum I
10,067
66.6
UO- U9.9
285
5.5
50- 59.9
190
U.7
60- 69.9
116
3.U
70- 79.9
111
3.7
80- 89.9
53
2.1
on oo o
6*1
1.2
IkO
Reference stratum II
780
20.6
100-12lw9
61
3.0
125-1U9.9
38
2.2
150-17U.9
28
2.0
175-199.9
6
0.5
200-399.9
28
3.1
60
Reference stratum III
161
10.8
Reference stratum IV
8
2.0
8
(U00 and over)
Total
11,016
100.0
786
Source: Fruit and Nut Acreage Enumerative Survey.
S £LI5AT
to iecfnu/14
T
39 JfU/OO
£*<i -x.o
o « r
o o r AT
Q.-PS -OS
X ITIlf Jf^ "J w 90f .9^£0 JS.'I
! e£ 5
Ob
■ oV
Id
3S
d
9S
qJvI-0$I
Hi mucfBi^a 'aofle-wlafl
■
O.S ' ;
1
VI aonetsloJ!
(isvo fans OOjJ). .-.
d8y
— i
.^avrtxiS svi.tr. tactynSf agaatoA -toif bffc
8.
It is well known that, for equal (over strata) per-unit costs of measurement,
a substantial reduction in the magnitude of a T may be secured, provided strata
variances, a , vary widely by using the Neyman "optimum" allocation-!/
R
(5) n° ■= nN o 1 / 2 II, o\'
r r r ' , h h
h
in which CT ^ = a,^/ N^/ (II - 1 ). Experimental evidence provided by Sukhatme-/ also
indicates that near optimum results may be secured by replacing the population
standard deviations a} in (5) by sample estimates 8. . The results cited in the
n n
tabulation below show that the actual sample sizes for the first three reference
strata do not differ markedly from the near optimum sample numbers obtained using
R
(5a) n ' = nil s / 2 H. s,
r r r . h h
h
for some of the important items of the final survey in 1951.
Estimated Optimum Allocations
(1951 Final Survey Data)
Reference
strata
Optimum sample numbers for
1951
sample
sizes
Raisin
production
Acreage
harvested
for raisins
Raisin grape
production
Bearing
acreage
I
596
583
616
622
578
II
120
m
98
86
1U0
III
62
71
6k
70
60
Total
778
778
778
■
778
778
2. Ratio (stratified) . With stratification, two forms of the ratio estimate
are possible
(6) t (1) = z iXA
h
and
(7) = § Z N h Y h / 2 N h X
1/ Neyman, J. On the two different aspects of the representative method.
J. Roy. Stat. Soc. 97:558-625, I93k»
2/ Sukhatme, P. V. Contributions to the theory of the representative method.
J. Roy. Stat. Soc. 2:253-268 (Supplement), 1935-
.jrreMBe'tt'-ii&sffi lo sizes ^+xfb•-1eq {BiatiB isvo) Laifp© .iol t .tsdi nworat ilsw ai il
Bis-sia bsbxvoiq t b5»n>r>;?a ©d ysc «b lo abyjinaBre ©rut nx no£tobfe9*' {slirtsiadifa s
^inoiJBOoils "mxfflu-fqo'' nem^sK orii anieu \d \Iebiyr \rrsv < jo .seansiisv
| \ ht Mm - °a (5)
•
\o • r; : .
oa Is x ism.+srt>lBa \6 bsbivo-rq s>on©bxv© Isinsm i"ieqx3 ,( l - u)\,Jl V .© * doxiiw 1U
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erti ai b©Jlo eilx/eea ©dT . rf a aotfsmiiae ©Icpuia ^d (5) nx l .x> ano ri&iveb bisbfie-ta
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boaxGico aTedraxm ©Iqnuaa mxnniiqo -xegn ©d* fno*ri YLbeifrsw i©llib ion ob sis-iie
cii y^niia Isnll ©ricf *c asasKti insj-foqrnj: ©rii lo ©ffroe ioi
anoxisooll A muraxtfqO b^emxj's.I
(stall ynvw3 Ifini-? £&1)
| XSSI
■
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•anxiRSU » 60TB13 nxa re/;
oraxsF.
©oim©l©5I
ar*.>±?<
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db
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8TV
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.boriJsm ©vi jsinssViq&i ©rii xo aioe-qas irtsiexlifo owd-erii nO : .1, t xieary,9V!
.4^1 t5Sd-8^:t£ .o?a -ifi^a
.boriiera' sviaajnoseiq©-! ©di lo yrioerfi ©ri^ oi.Bn^i-^ydxiifioO .1 t ©«Kh;n'jiua
9.
in which Y^ is the current year sample mean in stratum h for some item, X^ the
corresponding mean for the preceding year, £ h is the population total for the
item in stratum h f or^preceding year, and £ the over-all population total for
preceding year ( £ = 2 g )» Estimate T^ 1 ) is to be preferred if ratios differ
h h r
substantially from stratum to stratum; however, its use presupposes knowledge of
strata population totals, Since the latter is not known (except for bearing
acreage, 1950), the second form of the ratio estimate was employed in all cases
for which the ratio estimate was computed, X representing the 1950 and Y the 1951
data.
As is well known, the ratio estimate is biased unless the regression (of Y
on X) is linear and through the origin.^ The bias, however, is presumably neg-
ligible for large sample sizes. The mean square error of that is, E(T^-t]) 2 ,
is given approximately by
in which r\ is the current year population total (which is being estimated) and
^"xyh is t ^ ie P°P u l a tion correlation coefficient between X and Y in stratum h. The
estimated standard errors of the ratio estimates shown in Table k were obtained
by substututing in (8) the sample equivalents of the population parameters t) ,
£, ct 2 , a 2 , and , .
xtf yh' ' xyh
3. Difference ( stratified ) ♦ This estimate, also linear, is of the form
(9) + ~\h
h
and is, obviously, unbiased. Its variance is
(10) ^ = 2 II 2 (N h - % )(a 2 h ♦ a 2 yh - 2a xh a yh p^)/^\ - 1%
2
An unbiased estimate of a 7. is given by
(U) V " t V N h - \><4 * 4 - 25 xyh )/n h
d h
1/ Cochran, W. G. Recent developments in sampling theory in the United States.
International Statistical Institute. Proceedings of the International Statistical
Conferences. September 6-18, 19^7. Vol. Ill, Part A, pp. kO-66.
edj- n -X t nrsii emoa lol rf fficreixa nj nean MflMM tb&\ inantfo ?dx aX J rising' ac
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>jd TfX'e'dsmxxo'tqqa nsvrg ax
bns (bsirjnxia© goled ax rioxdw) Xsjo.j nor.jBD.rqoq ise^ inn-rajo edi ai jt rioiriw nx
eril ,d mniciJa nx Y bns X n»ew^od ins»xoix1?o3 norisXenoo noxioXx-qoq srii ax j„J°S
, n- ate.i9rairxsq noxj-sXiiqoq E»di lo a.+naievii-fpa eXqiriBS vdj (ft) nX gaiii'di/isdija ^d
:>da£x r -(m-
-.x bnfi
Yd n«»vxg ei lo 9ifiBiLf35» beafiidnt; nA
(XI)
,35^a?8 bsv-JxnU srii nx xtosdj ^nil'jmsa ni a^nanqoldveb inpo^Ji .0 .H ,fi9idao*3 \X
XBolisxifii2 XfirraiiBnisinl frix la snn.tbasooil .siydx-tanl leox.tsxisia lenox-tsm^
10.
R
in which s , - z(X - X, )Y /(n - 1). The estimated standard errors of differ-
xyh ? v hi h' hi h
ence estimates shown in Table h were computed using (11).
Estimates of Bearing Acreage
Estimates of bearing acreage of raisin- type grapes (Thompson Seedless, Mus-
cat, and Sultana) for 1950 and 1951 are shown in Table h> Orchard records place
the 1950 bearing acreage of these varieties in the seven surveyed counties at
217,7^8 acres as compared with the sample expansion of 215, Ul7. The ratio of 1950
bearing acreage of Thompson Seedless, Muscat, and Sultana varieties of grapes in
the state to that in the seven sample counties is 1.0558. Expanding the sample
estimate by this factor and adding the 3,990 acres of Zante currant and other
raisin varieties yields 231,1*27 acres as an estimate of the 1950 bearing acreage
of all raisin-type grapes in the state. This indication compares favorably with
the official estimate which is now placed at 233,888 bearing acres for 1950. It
will be noted that the computed standard errors of the seven-county estimates of
bearing acreage for 1950 and 1951 are a little over 2 per cent. However, the
standard errors for Muscat and Sultana varieties are relatively much larger and,
particularly for the latter, are so large as to make it inadvisable to prepare
separate estimates for this variety without increasing substantially the size of
the sample or changing radically the sample design.
Estimates of Acreage Harvested for Raisins
The relation between bearing acreage per unit and acreage harvested for
raisins (natural dried and bleached) for 1951 is shown in Table 3« These data are
intended to provide an indication of this relation for the population of raisin-
type grape units which was sampled. Hence, the entries (percentage frequencies)
in this two-way table have been adjusted for differences in sampling rates of ref-
erence Strata I and II (Stratum III was enumerated for the final survey which pro-
vided these data). Some interesting facts emerge from a consideration of this
table. Almost h0 per cent of all raisin-type grape units did not produce raisins
in 1951. Nonproducing units ranged in size from smallest to largest. Thus, U9
per cent of units containing 100 or more bearing acres and U6 per cent of units
containing fewer than 10 bearing acres did not harvest for raisins in 1951. Of
the units producing raisins, about 85 per cent produced to full capacity, that is,
harvested all of the bearing acreage in their units for raisins.
Linear estimates of acreage harvested for naturally dried raisins in 1950 and
1951 are shown in Table U. These estimates are subject to a relatively larger
sampling error (about h per cent for 1951) than those of bearing acreage. Acreage
harvested for natural raisins in 1951 was indicated to be about lh per cent larger
-rollxb lo gsorxe biebneJe bsisraxJas 9riT . (I - _it)V ,Y( .5 - , X)s « . s rfoxrirr ni
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fol baH&rt&d 9^fi9ioB boa &xwj agaeioa gniiasd n99«»ied nft&teie* edT
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^4 ,audT .cfaegiBl oi Jaallfii^ mortl ©sia nx beijces adxnu snxoxrboiqnoM ni
aixnxf lo inso i&q dd bns e?-rj£ 3niis9d srcom 10 001 aniniainoo aiinu inao 190"
10 *IcJ°I at aniaiBi iol iaeviart Son bib bsiob gniiaad . CI tisrii *ie?wel gnxn iB*noo
ai *an* t Y,iioBqBo XXol oi baotrbotq in9o t<?q 5 P - d-oods ,aniaisi gniouboiq aixrttf erid
.anxeis-i ciiny liotli ni e<$&en-*s gniissd edi lo XIb b9*at»>riBd
►nfi 0^ C I ni sniaxBt beiib ^IlBiuisn lol bsisoviBd ygcoioa lo aoJemid-?.? isaniJ
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TABLE 3
Bearing Acreage and Acreage Harvested for Raisins, Three Main Raisin Varieties,
Per Cent cf Units in Specified Acreage Classes —
Seven Counties Surveyed, 1951
Acres
harvested
for
raisins,
1951
0.1- 9.9
10- 19.9
20- 29.9
30- 39.9
40- 49.9
50- 59.9
60- 69.9
70- 79.9
80- 89.9
90- 99.9
100-124.9
125-149.9
150-174.9
175-199.0
200-299.0
300-399.9
400-499.9
Total
16.60
0.1-
9.9
14.02
10- 20-
19.9 29.9
13.86
2.20
21.92
30.62
37.98
4.49
0.83
1.87
5.91
30-
39.9
2.81
0.15
0.69
0.84
40-
49.9
50-
59.9
4.43
1.24
0.16
0.06
0.26
0.38
0.78
13.10
8.92
0.74
0.06
0.32
0.06
0.22
0.06
2.88
60-
69.9
70-
79.9
0.77
0.51
0.06
0.10
0.01
0.01
2.23
0.21
0.01
0.06
0.11
0.11
0.19
0,88
Be aring acreage, 1951
80-
89.9
0.26
0.06
0.06
0.01
0.06
0.44
0.94
0.07
90-
99.9
100- 125- 150-
124.9
0.18
0.01
0.02
0.54
0.21
149.9
0.23
0.02
0.01
0.01
0.02
0.01
0.02
0.08
0.08
0.02
0.20
174.9
0.70
0.20
0.02
0.02
0.01
0.01
0.01
0.03
175-
199.9
0.10
0.01
0.01
0.02
0.01
0.07
0.30
0.22
0.06
0.01
0.01
200-
299.9
0.02
300-
399.9
0.16
0.01
0.10
0.01
0.02
0.01
0.02
0.23
0.02
400-
499.9
0.04
0.02
0.01
500
and
over
0.02
0.02
0.07
0.01
0.05
Total
0.01
0.03
39.17
20.08
24.99
7.24
5.18
l.OS
0.82
0.3O
0.52
0.16
0.04
0.24
0.06
0.08
0.05
0.02
0.02
0.02
100.00
NOTE:
Percentage frequencies are adjusted for differences in sampling rates of reference strata.
HOLE* £ex,ceijcff&! ixinSneircjGii no rg^nz^g tot g7tt.01.om:©
QJTJJE. J.U.
■■•-'ii i r~
ro
i:-o-
TOO-.
- d : j
90-
83 *3 1
iO-
ia*a ■{
eo-
etra
ao-
e&*a
so-* <fd'a «
50-
sa»e
so-
sa # &
jo-
J3*a-
3TS 1
'©•■' f
yci.cs
"'a
0"T-
r T^a
■jo- ■
S*88|S*S3
10'
0*98 0*9<f tO*N
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0»ST 0*i0 !
vr. •
0 B J0
0*S2
0*0i 0*0!
f 0"0S j O'OJ
- jO'OG
j'CJi j
)*0J- 0 , JJ 0 # 0J
0*07
-4- — L . 4-
e p'oi p*oe i
j b - sTjo # 'je!o # ie
0*OJ '
0*C9
O'OS
0*0J'
0*01
C»0I
O'OS
0*07
O'OS
0'S2
O'SOl
0*01 0*01 ■
O'OJ
$01 CIO 0 # OS j 0'J9 -0*05
G # 0*
o*os
' r L..L 1 J f r 1 } I'
200
BesriruB yctoeSe arrg yotecrSo g*x.A62pog 4,01. jfirjeTire* Jpi.ee H^T" BffTaJir A^tre^TeQ'
K 2
TABLE 4
Acreage and Production Estimates, 1950 and 1951; Raisin Grapes and Natural Raisins, Three Main Varieties
Seven Counties Surveyed, 1951
_Tyjpe of estimate
1. Linear
2. Linear, stratum
III enumerated
Linear
2. Linear, stratum
III enumerated
1. Linear
1950
Thompson
Seedless
Muscat _
Sultana .
Total
Point
estimate
95 per cent
confidence Thompson
Inter v al 1 Seedlea g
jL__Bearing Acreage
acres
1951
Muscat
Total
Point
Suit ana J estimate i nterva l
95 per cent
confidence
173,663 |38,S24
(4,274)
(2,773)
5,130
(506)
206,720-
224,114
172,480
(4,315)
173,614
(4,138)
II . Ar;rfla£g_Harveste d for Natural R aisins
acres
202,996-
220,770
202,576-
219,714
86,214
4,538
984
91,736
(4,207)
83,490-
99,982
98,353
(4,197)
97,583
5,225
(1,001)
5,153
(4,022): (998)
1,318
(320)
1,318
(320)
104,896
(4,581)
104,054
(4,211)
in, Preharye st^roducj^n^orec^
t ons, fresh weight
96, 309-
113,483
95,800-
112,308
1,292,574
220,246
16,250
1,529,070
(38,782)
1,453,057-
1,605,083
(Continued on next page.)
H
TO
pxircsx
HI 6!JflBT6T.3f9q
! .«* ■
■
HI GIir8BGX.sr.r©g
5* .F7»e?J.'' Efi.ffrrrar
1 — —
LlS'sefi $S'9Stf
(80C)
esf imafe
J8*S80
do o<?5
[is
38*382
j * (338)
(r'oox)
8*SS8
( sso)
j'STS
(2S0)
T'SJ8
j 7X^*209 '
J J ** Vti« *
•fiSuWT^rTS^tsir— - " ^4
«»T88)
Table 4 continued.
' 1950
1951
Total I
Total
Tvne nf estimate
Thompson
Seedless
Muscat
Sultana
Point
estimate
95 per cent
confidence
interval
Thompson
Seedless
Muscat
Sultana
Point
estimate
95 per cent
confidence
interval
— — -- „
IV. Total Production
tons, fresh weight
1.
Linear
1,104,719
171,585
14,398
1,290,702
(33,772)
1,224,509-
1,356,895
1,445,083
(41,537)
223,857
(18,442)
20,060
(3,276)
1,689,000
(42,702)
1,605,304-
1,772,696
2.
Linear, stratum
III enumerated
1,452,322
(40,437)
210,674
(16,367)
19,500
(3,203)
1,682,496
(41,436)
1,601,281-
1,763,711
5.
Ratio
1,638,007
(20,031)
1,598,746-
1,677,268
4.
Difference
1,687,485
(19,598)
1,649,073-
1,725,897
V. Production of Natural Raisins
tons, dried weight
1.
Linear
130,149
4,166
1,274
135,589
(6,689)
122,479-
148,699
196,319
(8,929)
6,906
(1,345)
2,252
(564)
205,477
(9,103)
187,635-
223,319
2.
Linear, stratum
III enumerated
195,138
(8,661)
6,837
(1,342)
2,252
(564)
204,227
(8,839)
186,385-
222,069
3.
Ratio
203,914
(6,129)
191,901-
215,927
4.
Difference
204,446
(5,469)
193,727-
215,165
Expansions for 1950 are based on pre-
HOTE: Numbers in brackets are estimated standard errors of corresponding estimates.
harvest survey data obtained in August, 1951. All expansions for 1951, except preharvest forecast of production,
are based on final survey data obtained in September and October, 1951.
ITT GurajjeLO',
: T52 s J2e'
{ .. J20*TfS
f
t ,
7*?3S*25$
[8* Fjiieoi* efts
,.
TO' 200
-
14.
than that in 1950. The comparable increase in production of natural raisins was
about 52 per cent as shown by other data in Table h and about 6k per cent as shown
by current production check data. This suggests that increased yield rather than
increased acreage is primarily responsible for the large increase in production of
raisins in 1951. Sample data indicate, in fact, that yield increased by about one-
third. The linear estimates of acreage harvested for all raisins (naturally dried
and bleached) are 9^,950 (U,226) acres for 1950 and 108,136 (U,33U) acres for 1951.
The figures in brackets following the estimates are estimated standard errors.
Since the final disposition of a crop purchased outright in fresh form from the
grower may not be known to the latter, estimates of total acreage harvested for
raisins are subject to a downward bias. Indications are that bleached production
in 1951 was underestimated from the sample by about 60 per cent. The linear esti-
mate of acreage harvested for bleached production was about 3,1*00 for 1951. Thus,
the relative magnitude of the downward bias in the estimate of total acreage har-
vested for raisins is apt to be between h and 5 per cent.
Acreage Intentions
The preharvest survey in 1951 included a question on acreage expected to be
harvested for raisins during the 1951 season. Table 5 shows the relation between
acreage intentions for 1951 and acreage actually harvested for raisins in 1951.
As in Table 3> the percentage frequencies were adjusted for differences in sampling
rate of the reference strata. The slight differences in the marginal frequencies
of harvested acreage in Tables 3 and 5 are accounted for by the fact that Stratum
III was not enumerated in the preharvest survey so that, unlike Table 3, the rate
at which Stratum III was sampled had to be taken account of in the construction of
Table 5. It will be noted that for almost 25 per cent of raisin- type units, har-
vest intentions were not definite enough to be specified numerically at the time
of the preharvest survey. For other units, the agreement between harvest inten-
tions and harvest performance appears to be quite good. On the assumption that an
entry in a diagonal cell of Table 5 indicates equality of intentions and perfor-
mance, Table 5 shows that for approximately 86 per cent of respondent units, the
agreement between intentions and harvest performance was exact. Similar impression
is derived from Table 6 in which it is possible to compare by reference strata the
acres intended to harvest and the acres actually harvested per respondent units.
The agreement between these averages is excellent.
Table 6 also makes it possible to compare, by reference strata, the harvest
Performance per unit, for both 1950 and 1951, of the 1951 units with uncertain in-
tentions (hereafter termed D.K. units) and the remainder of the sample. For both
seasons, acreage harvested for raisins per unit was substantially smaller for D. K.
M
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TABLE 5
Acreage Intentions and Acreage Harvested for Raisins, Three Main Raisin Varieties;
Per Cent of Units in Specified Acreage Classes —
Seven Counties Surveyed, 1951
| Acreage
harvested
for
: raisins,
Acreage intentions,
1351
>
!
~ Un-"
certain
0
' o.I-
9.3
io- "
19. 9
20-
29.9
50-
39.9
40-
Cn
50-
53.9
60-
69.9
DTI
on n
on
yu-
no o
yy.y.
l nn
"1 O /I C
125-
i en
J.OU—
xi 4_.y
J- 1 O—
TOO O
200-
2^9 9
>~
ouu—
^OO Q
400
499.9
Total
j 1951
■
0
(0.1- 9.9
: 10- 19.9
14. S2
3.68
3.83
1.18
1.23
1.75
13/75
0.36
0.38
1.00
18.93
0.86
0.56
0.59
0.11
0.05
0.05
39.24
20.02 j
24.99 {
20- 23.9
1.42
0.18
0.09
0.23
5.21
0.05
0.05
7.23 j
i 30- 39.9
0.69
0.18
0.05
0.12
4.02
0.05
0.05
5.16
i 40- 49.9
| 50- 59.9
0.05
0.11
0.03
J. 05
0.64
0.u3
0.05
0.03
I-m!'
U04
i 0.80
i 60- 69.9
! 70- 79.9
• 80- 89.3
0.05
0.05
0.05
0.05
0.03
0.05
a. 44"
0.08
0.28
0.49
0.16
i 90- 99.9
100-124.9
125-143.9
150-174.9
175-199.9
I200-2S9.9
|300-399.9
|400-499.9
0.03
J. 03
0._06.
0.05
oTIs"
[
0.08 j
0.27 j
0.03
0.03
0.06, j
0.03
0.03
0.01
0.03 j
0.04 i
I
0.03
0.05
0.06
1
0.03
0.05
1
1
0.01 .
0.02.
! Total
1
24.53
23.76
15.93
21.19
7.17
t -
4.02
1.17
0.74
0.31
0.54
0.11
0.13
u . ..
0.16
— —
0.06
0.06
0.03
0.07
0.01
0.01
100.00
I j
NOTE; Percentage frequencies are adjusted for differences in sampling rates of reference strata.
H
Cn
L
r
1
■ ■
Q"02
L" -1
! SO- 8c>'3
0*02
1 !
1 jo- cva'a
€0- 6c» k d
O'Oy
a* it
so--
TO- Td'd
n j- .9* j
o- I8
;••
Mb m
O'Oe
O'TI
xt\i j 0 T fcj 2 I fliT* - 1 '
OT-j
rOJJ? 3T7CJ \
TABLE 6
Bearing Acreage and Acreage Harvested for Raisins
Respondents and D. K.'s, Seven Counties Surveyed, 1951
Proharvest and Final Surveys
1950
Bttt s , J D. K .'s __
1951
Bearing. Acrep_ Per JJnit '
a/
14.7
54.7
113.4
15.3
54.8
158.9
Acres Harvested for Raisin .Per, IJn
it*/
4.?
18.4
20.8
9.7
27. 2
55.8
14.7
52.8
115.8
4.9
22.0
20.8
Acres Intended to H arvest P er Unitg/
9.9
28.9
55.5
Per Cen t of Bearing Acr es Harvested for Ra isins
62.9
8
35.1
a/ Preharvest Survey, August, 1951.
b/ Final Survey, Sopteiiber-October, 1951.
■r
•
8.*S5 .
1 NS
[
1 i
! s.^x
II
III
8.33
I
II
\ 1 313*
II
III
3 fix " x aT I
i 0,31
I I S
J..UG j
1
17.
units than for respondents. One possible explanation is that on the average the
bearing acreage in D. K. units is smaller than among respondents, although some
control over size of unit is imposed by the use of reference strata. Table 6 in-
dicates that the average size of unit among respondents is slightly larger than
for D.K. units in Reference Strata I and II and substantially so in Stratum III.
These differences, however, are not large enough to account for the markedly larger
acreage harvested for raisins by respondents. Differences between percentages of
bearing' acreage harvested for raisins in the two groups of units parallel, in fact,
the differences in means. The inference seems unavoidable, at least with reference
to 1951 data, that operators responding as uncertain to questions regarding inten-
tions will on the average allocate a smaller acreage to production of raisins than
operators whose preseason plans are definite.
Production of Raisin-Type Grapes
Linear, ratio, and difference estimates of 1951 total production of raisin-
type grapes in the seven surveyed counties together with estimated standard errors
are shown in Table U. It will be noted that the standard errors of both the ratio
and difference estimates are about half the standard errors of linear estimates,
even with Stratum III enumerated for the latter, but not the former. The standard
errors are relatively quite small, amounting in the case of linear estimates to
about 2.5 per cent and in the case of ratio and difference estimates to about 1.2
per cent. Linear estimate for 1950 is also shown in this table. Multiplying this
estimate by 1.07^1, the ratio of 1950 bearing, acreage of all varieties of raisin-
type grapes in the state to the bearing acreage of the three varieties sampled in
the seven surveyed counties gives approximately 1,386,000 tons fresh weight as an
estimate of the state production of raisin-type grapes. This estimate compares
favorably with the latest check figure of 1,326,000 tons for 1950 as given in the
1951 December California Fruit and Nut Annual Summary. Applying the same expansion
factor to the 1951 sample estimate gives an indication of l,8ll;,000 tons which can
be compared with the current official estimate of 1,805,000 tons.i^ Official esti-
mates of production by varieties are not made.
In the preharvest survey, the operators were also asked to indicate the pro-
duction of raisin- type grapes expected on their units in 1951. As can be seen from
1/ This expansion method assumes that the yield per acre in the counties surveyed
is the same as in the nonsurveyed counties and that the yield of nonsurveyed varie-
ties is the same as of the varieties surveyed. Data from other grape samples
obtained at the same time as the raisin production survey data indicate a lower
yield in the latter counties.
ori.t erii no 3.
•iiR03 rtgoorl.t.ls t a^ni<
-fii d slieT .s .texts
3i noicfwrjlqxs :<Io\taaoq s»f.O ^im4»mqttn
^noms nsdi -islijejrs ai siirdi .71 .(! nl |
vrflsn |gj 9eu stii x<t beaoipi: a/ ^inx; lo &s.
i9%i&i y^rigila t| ad-n^broqaei ino<tte .ixnu lo psxa s^eiav* e*ri:
• III ni/iBi.t':, nr o3 ^rieivtnsi-i JtfQ bits II iycta I s+fiiiS sone^cleE nx «
isgiaj. ^Ibs'MasiT ftii iol chxoons otf t-^juons Sjisi ^on.st^ t wvsfc*ori ««s>or
lo segednsoi.^q neevttd aaona lolled .adrtebnoqa-.n .ani a is $ iol b«>i?
ttafll nr tlellKisq aJxat/ lo aqi r OT;j owi «rtl nl anisisi *tol b*te?Yi6n &*
9Mtt&9 4 i&t tiivi ip.c&l is t ©idsbxo vsnif amours coasts!. il <?riT .j'.tsrt nf a<
-ne-tni jnxbits anoijaeu^ c} nis.+ison;/ as srubnc^aet aiotfSTeqo isrij
H||| aniaxsT lo noxiojboTq o& sgseios TsIIsnra -a iitotjjjjj eysTdvs ari*
.♦a^xni'l^b sis afij?iq. rroase3f>iq 9?
" * _ aoqstO dC^X-fijgxai lo rsoiS-nsfynl
-nxalsi lo r.olio'fbo iq Into* 12? L lo e^tsmii *.? aoiWiecliB bus .oiisi
sxlrtoo
»*soxi>
tfl not
oi.+e'i
| 3ioi'is» b-rsbnoja o>ii dsrid bsion
il lo ctotno r ^'tEbiiK^a (?ti$ llsrf
p?. co sitiJt nx ^n£ctnirc3B
'».t I ETC
iffa o»,If
cop <inJ
io 1 eif
ta e*t io
'--.sn.o.t
erii stfsoxbni oJ-
S.ror-tiTv:
18.
Table k, the linear estimate of expected total production is almost 10 per cent
lower than the production estimate secured in the final survey. When expanded,
as above, to a state total, it was 1.1 per cent below the September 1 official
estimate. There is little reason to question the significance of the difference
between the preharvest and final estimate. As the tabulation below indicates,
production was underestimated in the preharvest survey in each of the reference
strata.
Expected and Realized Production of Raisin-Type Grapes
Reference
strata
Expected
production
Realized
production
tons, fresh weight, per reporting unit
I
112
II
396
U20
III
1,075
1,187
IV
3,77U
U,076
Production of Raisins
Estimates of production of raisins shown in Table h for 1950 and 1951 refer
to naturally dried raisins. As in the case of total production, the ratio and
difference estimates have substantially smaller standard errors than the corres-
ponding linear expansions. The apparent superiority of ratio and difference esti-
mates is maintained even if the standard errors cf the linear estimates (but not
of the ratio and difference estimates) are recalculated using a stratification more
nearly resembling that actually employed in drawing the sample. Thus, the standard
error of linear estimate of natural raisin production in 1950, using the finer size
stratification of Table 2, is 6,329 tons as compared with a standard error of 6,689
tons computed on the basis of reference strata (see Table h) ■ This reduction is
rather trivial in view of the increase in the number of strata from 3 to 15.
Linear estimates of artificially dehydrated production using the 1951 survey
data are 10,73h tons (dried weight) for the 1550 season and 7,U-7 tons for 1951.
Check data indicate bleached production of 17,758 tons for 1950. The latest avail-
able figures on deliveries in 1951 sum to 18,060 tons (Raisin Administrative Com-
mittee Seasonal Deliveries through August 2, 1952). Thus, for both seasons, 1951
survey indications very substantially underestimate bleached raisin production.
Estimation of the latter was not an objective of the raisin production surveys and
the cited indications are an incidental by-product. Estimates of bleached raisin
.81
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9onei9llxb arid lo eonsoilingxa 9rid noidasi/p at noasei sXddiX el 9ir*riT .9j«mii39
,e»^soib«i fcoisd no Idsludsd ?rid sA .sd'-rnxdss Isriil hns dgsvisrisiq odd neswdec
sonsislei srid .lo rises nx .y.sviwe dasnsrieiq sfij nx bei-smlvtapiebnu e-.-v noxdoi/boiq
.sdsida
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C8d t d 1c ions fnwbnada b ri*iw b&iBqmoo as anc* el t S sIiteT lo noidsollidsida
ei noiiMjbsi axrlT ,(6 sIo'sT 9^3) Bcteitfe scnsielsi lo aiaBd etii no bftai/qpoo ano<f
t^X oi £ moil cisijs lo ledmua erii at ezBsiioni erii lo waiv ni Islv tii lerii^i
Tt?vix;3 It^l 9ri* snxai/ noiJowboiq bsisibvisb x£i&ioi1liiB lo aatanixia9 issnlJ
•X^l lol 8«©i VI4«V bfiB noa.G9a 0^1 srfd 10I (irigiew bsiif)) enoi iiCV«CX sib siBb
-iiBve +asi£X eriT .05^1 lol Bno.+ ^c!YtYl lo notior/boiq bsriofir id ctsolbni BtBb -doed!
hbroD evl.tBiiainliaI>A nislsH) enoJ OdO^I od muz X^<?X nx asiiovxl&b no 39103x1 pMb
XKi' «eno239a ridod 10I t at/riT . ('i^QX t S iex'-jaA rfs«oirti "esfisiviXsn XBnoassc -isdtim
.noidoyboiq niciBi berioscXcf 9.tBntliaeishntf Y-t-tBxdi-usJadxfa ytev enoiis«)Xbni ywma
bns a^vixra noidsufooiq nlalsi srii lo ' svxiost.do ns don bbw if.-ddel srid lo,. noidfitiu ,ta3
nislBl b3doB9Xd lo asdBffidBfl ..dotiboiq-y'd I^.tnsblonl ne 9ii? anoidsoibni bsdia 9dd
19.
production published in the reports of the raisin production surveys for 19h9,
19^0, and 1951 were obtained from separate enumerations of production in dehydra-
tor plants and dry yards.
How accurate have been the survey estimates of natural raisin production?
The estimate for the 19U9 season was based on a survey of only four counties and,
thus, a direct comparison with check data is not possible. However, the 1950 pre-
harvest survey linear expansion for natural raisins produced in 19h9 of the three
varieties surveyed was 23h, 16k tons compared with the currently checked production
estimate of 235,376 tons. The latest available check figure on 1950 natural rai-
sin production is 13h>665 tons dried weight which represents deliveries to handlers
to July 5, 1952. The linear estimate based on 1951 survey data is 135,589 tons
(see Table h) and is within 1 per cent of the check figure. Further comparisons
based on various estimates from the October, 1950, final survey, estimate released
on October 19, 1950, and their difference in per cent from check data now avail-
able are as follows:
Estimates of production of
natural raisins, 1950
Thompson
Total*/
Differences
Type of expansion
Seedless
Thompson Seedless
Total*/
dried
tons
— ■ 1 1
per cent
Linear
122,111
127,776
-U.3
-5.1
Ratio**/
12li,713
130,ii6l
-2.3
-3.1
Ratio, revisedly£/
123,32ii
128,936
-3.U
-U.2
Survey estimate as
published^'
125,000
130,700
-2.1
-2.9
Recorded deliveries^/
to July 5, 1952
127, 65U
13U,557
0
0
a/ Includes Thompson Seedless, Muscat, and Sultana varieties.
b/ Computed using ratios of sample indications of production of natural raisins in
1950 to 19i;9 weighted by estimated 19ii9 production within reference strata.
c/ Based on revised estimate of production for 19lt9.
d/ October 19, 1950.
e/ Raisin Administrative Committee, Weekly Report of Deliveries to Handlers.
f S4&I tot avpvtoa nojc^ifbo'tq ntzini s>At lo ach:oq3i en"* nJ bptetlduq noxtoirbonq
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'0'$ .BbisY one ainsi'q id
?nox*nL'fanq nxaisi x&ixi&n lo as^fimrtea sriof n<?od avari qIbiuohb toH
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-etq Oc^i &rf* ,iC'^9WoH .eXdi3aoq- ion ax b)b'o jfoorio ri,tiw rioeiTBqmoc +oeixb * ,?>xmS
©eutt arii ^i&l nl bsoubo'jq anxexert Isiuififl iol noianfiqxe -tsonxl y,9vdjs iaevtsri
aoiioubmq bailoailo ^XirteTn/i) t?rf* : riixw bcieqp'oo anoi 4dl\il£S qbw beysviaa -.lexiPxifiT
-is*! ictujeri Q?QX no a^tn}/! >'oarfo ©idsiisvfi isoJxi sriT .anoj oY£ t $€S lo PtetrJtiw
it»£ba&A o& aexisvxlefc ajneaeaqtrt rioxilw irf§iew bex*ib anod 5dd f 4fX ax noxjouboiq nx3
anoi $8&k«!£f ai sJeb fPfMtt X59X no beaed eisnii^aa isynil eriT .S5QI t 5 tXtfl
anoaxrtflqfioo tttfNpt « 9*1/3.1 1 jlocrt'o t>ri«jr lo inao icq I fliri.ixv a± bns (il oXdsT ©£»a)
baas^Xst aisnriias vYsvxt/a Iar.il ,.0$?! ^©cfotfoO s»dx wotl adtemxtfaa at/oiiev no beasd
-Ixb/b won Bifib jfoerio moil dnao neq ni sonet?- 11 ib tisdt bns ,05?X t 9X isrfotoC no
■ •,' :awo.Ciol S£ ©TB sXds
- r— : — • — —
^ i \_
1 iffif 1
jT 1 aa?XbsaS i
£'iW*h*hb 1
f 1
{
El' tXT (1 i5X
>ib=»^3 noeqnori? asfw/XonJ \b
iq lo anoxisoxbni; olqmse lo aoiisi ^nxau be«t»/qmoO \d
.9i5?X nol rroxdonboiq lo f.jsmxd'ae bo«».xve»i no D9Bb8 \a
20.
Present indications are that the October final survey estimates for the 1951
season are not quite as satisfactory as those above for 1950. Seasonal deliveries
through July 5, 1952, of natural Thompson Seedless, Muscat, and Sultana varieties
as reported by the Raisin Advisory Committee amount to 220, k93 tons. Thus, the high-
est estimate for 1951 shown in Table i; is about 7 per cent and the published survey
estimate of 209,600 tons (October 10, 1951) about 5 per cent low. Of some inter-
est also is a comparison of the published estimate based on the October sample and
the estimate common in the trade at about the time the former was released. This
is shown below. It should be added that a measure is not available at present of
the accuracy of the check data used in appraising the 1950 and 1951 sample esti-
mates. The check data are still subject to revision for both years but even in
final form may not be completely accurate. Figures on seasonal deliveries are
based on reoorts from a score or more firms, all of which may or may not have the
exact data available at the time required or be able to distinguish receipts by
croo years in which produced.
Comparison of Estimates of Production of Natural Raisins From
Thompson Seedless, Muscat, and Sultana Variety Grapes
Season
Published survey
estimate^/
Estimate common
in traded/
Present check data
indicationc/
Per cent difference
Survey
Trade
dried tons
19h9
226,300
259,000
235,576
-3-9
9.9
1950
130,700
135,000
13ii,665
-2.9
0.2
1951
209,600
235,100
220, U93
-h.9
6.6
a/ California Crop and livestock Reporting Service, Dried. Raisin Production Survey
(November 3, 19l9)j Estimated Raisin Production— 1950 (October 19, 1950); Esti-
mated Raisin Production— 1951 (October 10, 1951).
b/ California Fruit News, November 5, 19u9 (p. 6); October lU, 1950 (p. 6); October 6,
~ 1951 (p. 6).
c/ Raisin Administrative Committee. Weekly Report of Deliveries to Handlers. The
check figures shown for 1950 and 195l represent seasonal deliveries (sweatbox
weight) through July 5, 1 Q 52 of natural Thompson Seedless, Muscat, and Sultana
raisins.
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' 000
, , . .
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j
21.
Wi thin-Season Estimates
The primary objectives of the two within-season surveys was to provide infor-
mation on prospective tonnage of natural raisins and acreage being harvested for
raisins to specified dates while harvest was in progress. The two surveys made
each season were one week apart. In 1951 reports were issued within 3 days of the
starting date of each survey. In order to reduce costs, one-half of the regular
sample of raisin-type grape units was utilized for each of the within-season sur-
veys; odd-numbered units provided the sample for the first survey and even-numbered
units were used in the second survey. In addition to tonnage of natural raisins
expected from grapes on trays and acreage harvested for production of natural rai-
sins, information was also obtained from operators on the acreage harvested for all
purposes, acreage expected to be harvested for production of all types of raisins
during the season, and the number of trays harvested.
Linear acreage and production estimates based on the information collected in
the within-season surveys are shown in Table 7. Estimates of 1951 bearing acreage,
acreage harvested for natural raisins in 1950, and production of natural raisins
in 1950 are also cited as control items. As was indicated previously, the estimates
shown in this table and the accompanying standard errors were computed using the
detailed size stratification of Table 2. It will be noted that the standard errors
of within-season estimates are roughly of the same order of magnitude as the stand-
ard errors of comparable estimates calculated on the basis of reference strata
utilizing the full sample (as shown in Table k). In relative terms, however, the
standard errors of the within-season estimates are rather substantial, particularly
for the first wi thin-season survey. Thus, the relative standard error of acreage
harvested for natural raisins is over 8 per cent (of the estimate) for the first
within-season survey and about 9 per cent for trays harvested and expected tons of
raisins.
As stated, information on production of raisins to specified date was ob-
tained in these surveys in terms of number of trays harvested and tonnage of rai-
sins expected by operators from grapes thus harvested. Neither item yields ob-
jectively the tonnage of raisins produced. Objective information on production in
dried tons, in fact, cannot be obtained until harvest is completed and most of the
raisins are delivered to handlers. However, these items are of some help in indi-
cating approximately the tonnage being harvested. It is of some interest to note
that using the customary 5.5 pounds of raisins per tray to convert trays into tons
of raisins gives consistently higher estimates of tonnage than production figures
obtained directly from operators (113,500 as compared with 108,100 tons for the
first survey and 192,600 as against 185,500 tons for the second survey).
zeiumtttp anss9?-niiit.rY, r :
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ni noxJoxi'ooiq no noxieanolrti cvi&o^ijSO .bgojubcnq eniaim lo essnnotf 9dx yXeviiogc
9itt io. Jbqib bns bg^aiqmoo ai ^aavnan Xidxm bonxBTdo ad ^oxWbo t io6l at ,an6i baiib
•tonx nx qX9rt araoa io sis smti 9z*rtt t iev9YJoK .eigXhriBri oi bo-ts-viXeb .9is snxaxBi'
'.-ton o& ^89*iijXnx oufoa lb al il .'b^eovifid ^nisd sgennat- snc: *{X 9isorrxo^qqa gnitcc
a- o* o*ni a^si* ^-lavrroo o* ypt& -igq aniaxAt lo gbniroq y/xboic+sxio 9d* gniai/ #sitt
esttra rl nciJoubbtq nsrii ^gBr,noi lo B9im3stz9 -langid 'xitr.sf?. ianoo bdvxs anxci«t lo
9d>t icl snoi OOX t HOX ri^i-v t>9TBqflfi^o as O^j^XlVeinlsisqo mcrl yl^oaixb bgrrxe^do
.(yavij/p bnocse %ritf-T.ol sno^ Ob5 t ^X tanxB^B es '06,^1 bns v^v*fua d-atil
TABLE 7
Within-Season Acreage and Production Estimates, Raisin-Type Grapes and Natural Raisins,
Seven Counties Surveyed, 1951
Type of estimate
Acreage
harvested
for
natural
raisins
i ut.ax
trays
har- ,
i -|&/
vesteds/
Tons" "of "
natural
raisins
expected
from grapes
harvested
""Total
acreage
of
raisin
grapes
harvested
Acreage
expected
to harvest
for raisins
1951
bearing
.acreage _
Acres har-
natural
raisins.
X X L/vXU.V' viUll
of natural
raisins,
JL
„ 2
3
. 5
7
8 ~_
.... acres
1,000
trays.
tons, dried
*
weight
acres
tons, orisa
weight
, i !
First Withia-Season Survey t September 4
Linear estimate
58,829
41,285
108,135
78,812
111,928
213,545
91,821
135,455
Estimated standard
error
4,839
3,698
•5,524
5,050
S,108
3,513
5,909
9,480
Socond Witliin-Season Survey, September 11
Linear estimate
93,362
70,040
135,432
117,206
111,569
216,091
96,586
I
140,303
Estimated standard
error
5,258
4,297
11,431
5,324
5,914
3,527
6*555
j 8,804
a/ At 5.5 pounds of raisins per tray, these estimates correspond to the following dried weight tonnages of natural
raisins: 113,534 (10,170) and 192,610 (11,817).
1
IPX.
sruq ?,
g 1
B*aaa
| - 1
i
in £*tos
2 v 2j2 (
&*60d
8TS TIT*oS8
6T*8ST
©&pcq ^,03. 1
j
23.
Production of natural raisins to specified date may also be estimated by re-
lating sample indications of number of trays or tonnage harvested to total produc-
tion of natural raisins in the preceding season. Such ratio estimates based on
reference acreage strata (competed using fojwula (7)) and their estimated standard
errors are shown in the tabulation below for the two wi thin-season surveys in 1951.
These estimates are somewhat lower than the corresponding linear expansions shown
in Table 7, particularly for the secono wi thin-season survey, and have also some-
what lower but still relatively large standard errcrs.
Ratio Estimates of Natural Raisin Tonnage
Expected from Graces Harvested to Specified Dates, 1951
Item
First wj thi n-
season, Sepremter k
Second within-
sea son, September 11
tons, dried weight
Tonnage from
trays harvested!'
112,775
183,611
Estimated^/
Standard error
9,058
9,803
Tonnage expected
by operators
107,310
177,871
Estimated
Standard error
——————————
7,806
9,552
a/ Reduced to tons at 5-5 pounds of raisins per tray. In units of
1,000 trays these estimates and their standard errors are hi, 009
O,20h) and 66,768 '3,565).
Survey Costs
The table below presents estimates of average miles of travel, average inter-
view time (including time of travel), mileage cost, and total field cost per com-
pleted schedule for the 1951 surveys. The latter average comprises all payments
to enumerators for time ($l.h7 per hour) and mileage (graded from 5 to 7 cents per
mile in calendar month). The average time and mileage cost for all surveys in
1951 was $1.82 per schedule; analogous average costs for 19h9 and 1950 were respec-
tively $2.38 and $1.73. The relatively high average for 19U9 can be attributed in
part to the fact that fewer enumerators were employed who resided in the locality
of their work and in part to the unavoidably higher expenditures incurred in the
location of sample units for the 19^9 preharvest survey. The 1950 and 1951 samples
in the four main producing counties consisted very largely of the 19^9 sample units
and, hence, these location costs were not reincurred in later surveys. Higher time
u'ci M
CS1 lB1U+£0
SW.CJfia txs
'ins aae&ai
XXd.£6X
;J ad* ax r
[v.amoa 9i£
TaX \Xavj:.J
a MH
&Mff!l agaiovB lo saXini agates 'la fcaJam-ttaa 8*naa<viq woXad aXda* edT
■ -im>$ iaq .taca Mail JC«fo.t 'brte eqcoLLn t (ieffftl$ 2o .sinl* gnihuloni) a.irii waxv
e?fti*r\caq III «98i:i<jpwjb '*8fif»vr> i.a<fctsX *rfT .spTOc X<$X ad* not aXirbaifoe beJaXci
taq atnaa V od r 1 inoYl babs*ra) a ?jaafJ« boa /i«orf ^aq V'J..X$) smirj' 10I a-xcJiTjaffuma o&
• ni «y.9Vwb iXa nol cfeob ag&i • xnr- : f>n$ emW'-.asrJeTjp edT ,(d*nom tabnaXsa fix aXxm
-aaany: aiew (ftp I bna iol ai?c'o sa'a-r^va- aot>?oXwfc ;ftXubarf38 isq S8 .X$ -as* X3^X
ni baWdi***** ad f»o'&&X'ioT aga-iava dgirf. ^XsvWaXo't adT .fc?.X$ tarn ffc.st v/evx*
«lxJac ; oX ad* nx bebia a'X orfw ba^olqma -a-iaw .eiadx'tami'na -i«wal tadt &o&l ad* o*.vhtcq
rjx bb*xuranx aanttfibnacpee 19^3 id . ?.5dabxoVamr ad* 0* toaq rix-bna tied* lo
aalqaaa '^S- bna O&'X adT "."^avida aaav-iBdariq r ^lPI «d* rto'i atxrrt/ aXqaies' lo noiitsobX
atfituf sXqsoae <?4°X adj "lo v;Xaai«X vrev bafobwtoo' aattnaor Sflxoubo*rq nctfitm' -iwcft ad* ni
9)ar* -i-;ri^iH .a^eVrure ••tatfaX rtX ba-.-'xrofl iba *on a*r©Yr ecrsco noxiaaof- saadtf t aanari t bnx
24.
and mileage compensation rates in 1951 account for the somewhat higher average
field cost in 1951 as compared with 1950. The total costs of the four raisin
production surveys varied from about $5,800 to $7,900 in the three years in which
they were made.
Enumerator Time, Mileage, and Cost Estimates
Rai3in Production Surveys—California, 1951
Per interview completed
Survey
Number of
interviews
Miles
traveled
Time in .
minutes^'
Mileage
cost
Time and
mileage cost
Preharvest
778
9.6
58
$0.6U
$2.05
First wi thin-season
389
M
U9
$0.61
$1.80
Second within-season
389
8.3
$0
$0.55
$1.77
Final
®&
7.7
U2
$o.5i
$1.52
All
$1.82
a/ Includes travel time.
b/ Satisfactory schedule returned by mail by 227 units.
Discussion
In appraising the experience accumulated in the raisin production surveys
separate, but of necessity brief, consideration will be given to questions of
sample design on the one hand and measurement problems on the other. Discussion
under the first heading will be restricted largely to an appraisal of the effi-
ciency of the stratification procedure emoloyed. Under the rubric "errors of
measurement" vail be considered the validity of basing acreage and production
estimates on responses elicited directly from operators rather than on objective
but more costly sample measurements and counts of acreage and crop. Problems of
measurement will be considered first since, in a sense, these are prior to and
more basic than particulars of sample design.
Errors of Measurement . The schedules used in the various surveys were brief
(see Appendix) and the information requested from operators was of a direct and
relatively simple character. Apart from questions dealing with intentions (acre-
age to be harvested for the production of raisins) and expectations (preharvest
production expectations and tonnage of grapes expected from grapes harvested), th
schedules referred to factual material. However, for the current year "factual"
questions, the operator, in most instances, was not himself in possession of pre-
cise information and at best could report only what to him appeared to be a
. ■■■ ^i i<pfc* r ggfc .tft?X-irf*t# ' b*q^pgg fftiiS&f at tecs bteft
sfosw «yt-y» vorfc!
je^h.-^ ,;^v?iJ!M «3»H ~&tef9atri&
*■ ~* rY^rrtlT»*t l~ *'*;~ T t' i ^*'^' gr ^ y ^** i ''* > ' *^ yt — -<.-v c ..4 .. -«-. —
IV. "■*• •■"»-■ • *.«S ' lit j'l .r.'JJt
i
.^e-njurtfrw bnodjS
.-1*129 fwi* lo Ifisintaris nK o* YlsgtsI ha&ofrttzen
It emldcnn wit) tm agA&toji to tftttuoir -lm eiffs
men srro r,tlf no jtg.rsyb oIcrn<£:sj
II.c.v Tjnxbsed Jain add- icbm'
hs-bfencs sd II jw "tfr^nr^Tvssswr
Pi3il9 eignoctssT no n^arcieft
•I/B<a3H '^1*300 3103! &ud
rt^&j-GRos ed XIlw ta&miL'&£Bx
•.7igxaf3b sfqittea lc. atuXfi-.^tga rtsd* Meed -«©i<i
bns .*j>:~ib | 'ir b** *io*Bt<>qc «#$ tefttWjgi* nH^olrt* bite ixitm.aqqft MB')
f ijttKf?)S-l' ! naoTt J-nsriWo iN# ^Hil-||j||^fiilfr' v •l^al 5 *** ^ «^ ^r-^^T A3lxf&&^oa
5o ffbxB'gseeoM rft iX^eusp, ^iif ^sfafrsrfi ia^- s>di. ^e/ro Ws^'p
b od od - f
•Vrf
l*66 ..f-ssd .b/iis m»
25.
reasonable approximation. This observation applies perhaps with greater force to
production data than to acreage since the magnitude of the latter (e.g., acres
harvested for production of natural raisins) is directly ascertainable by the op-
erator. Ordinarily, only a small proportion of the raisin crop is delivered to
handlers by October 13, the latest closing date of a final survey in the past three
years. In most cases, therefore, the operator's response to questions in final
survey on tons of raisins produced is inferential rather than directly factual,
based as it is on approximate translation into tons of numbers of sweatboxes,
field boxes, or other raisin containers. The same argument applies pari passu
to operator's responses regarding total production (in fresh tons) of raisin-type
graces although in cases of harvest completed by the time of the final survey for
uses other than the production of raisins, the fresh tonnage disposed through
commercial channels may be known directly to the operator. On the other hand, in
a small proportion of units the crop may not even have been harvested by the time
of the final survey.
Response errors will naturally contribute to the total error to which esti-
mates are subject. In addition, response errors may introduce a measurement bias.
There are indications that estimates of production of natural raisins based on op-
erator responses secured in the final surveys are, in fact, subject in some years
at least to a downward response bias. This evidence will now be briefly reviewed.
Information concerning production of natural raisins on sample units during
the preceding season was secured from operators interviewed in the 1950 and 1951
preharvest surveys. It is, therefore, possible to compare, for identical units,
production indications obtained in the final survey, at the time the actual weight
of raisins produced was still not available to the majority of operators, with
production figures provided some 11 months later, presumably based on all objective
information regarding quantity produced which could possibly be known to the op-
erator. Averages (per unit) for such comparisons are shown in Table 8 separately
for the 1°U9 and 1950 seasons by reference strata. For the 19U9 season, the dif-
ferences in production reported in the 19l9 final and the 1950 preharvest surveys,
are, on the average, small and not consistent over strata. For the 1950 season the
average differences are more substantial and are of the same sign in all strata.
On the average, the 1950 production of natural raisins was underreported in the
1950 final survey by some 8 per cent in comparison with the 1951 survey. The analo-
gous figure for 19ii9 is about 2 per cent. A further fact of interest is that
underreporting in the 1950 final survey was not independent of the quantity of rai-
sins produced on the unit. The data shown in Table 9 indicate that, on the average,
oi &*rtx>\ itfg&T$ H&iyt aqsd-rjq aaiXqac nc-jriswaedo. e&fP .troiiBiasy^if^B sld&noBS&t
29*10*; ,.3.^ t9&&B£-&A& lo Abif&lftsh» add rocte z$Rtnon ' od nerid- s*«fa ftoidat/bOTrt
~qc> sif.t ^d-'snifd^oss ^X.*o9ii£j -sr'- (shiR-isi Xsiud^in lo no-rd-atrfcoTcr toI bade 9 v%3d
od ber^VxXofc ex (pno'/ixeis* add nai^-jtjqwwf -Slam' b ^Xno-vtt&Bnttrtn ,*jct£io-
*?iddd8sq add fit iga*n/a Xanxt « "to ed*b g«iao£&-.d»ed6l kid ,££ *id staXbnfri-
XBntl ni snoids&xjp od aenonB-yi b •'locPst-aqo art* i9*jelaiadd ,398^0 daom nT- itressv
jXsudoM \XdD93xb nend laddrn'JaB.xdrianalni.ai' hzoubonn snj:a.p?*i lo efrod no vavtwj
t S3>:ocf;ts9Wa BisdJlfSB Id enod odnx ooidsXea^tvid sdfcmxXO > tqq£ no zi dl ae boBsd
ys . g*H ffi 8 ** 'g^zXqqB d*?aiMn|ue osibb adT ;8tsrrJtei.->oo nrsis-x lerido 10 t 8axod bXatl
sqTEt-nreJrjjrr lo (enod nearl • nx) noidoubotq X/idoi ?«±fnj?aat aoehoqesi a''iod.s~9Q-o of
'tol y i rtyff 'X snxl -add lo amid arid fcftdAXqjtwo; #S9TOsd lo b^sbo «r rigfloridXs $90^3
ri3foint* fosopaft ssmnod riaail 9-rfd K eK..eiz* 'lo- dol+onboia. add nor* J tarido aea,.
ni t bnx>d t*rido arte) - nO" .tocfjwsqo arid oi ^Xdoo-jib n*orof -©d y;m *>f anrsria- Xfrioi^.w
Mttd' eitd x'i bsdaWiBd- rood eved oava don \:sb"*|o*xo add stinut lo noidteqw? £.f"sme
-xda^' r.'Aito o'i iotd laded add od ad#dx**dnoo YXXsi»dj?n 1 1 tit &swt& ^enocfesS "
.a*rd draMtanriMr £ &$£fbo 4 Jdnx \£m -atoiia Bzaoqe^-i \ncirtbhB-ttX .deal-toa. «SB ec-dsw.
<-qo no bated 'enteim •XeiodBn 'lo noxdouboiq lo* esdamxd:* . dsdd 6iroidMihfsi e*ts aiad?-
sissv' 9ftoa nx daatdi/a t doal nx ^eis. b^vxmb ihnil add nx b-it&ooz ef-enoqedi •todsto
*b3we±v9's v/lexdd yd won XI x* e&dobxva exrfT .Bcxd Gaftcqeai btfiwwf* « rod tze#& dp.
fffiUrb Bdlflff \Co}3T53 no enieiat- /Bitfdan lo nofio/fboiq animvofloi nnxtnurtolhl
I^-I 'bns t)^QI eaid rif k^tm&titk . V9o$v*aq&'Blvt\ beurs-st sb-t hobB'su •■snitso.i'jq erid.
,a.'inj.' Iteoxdnobi *w>l " 1 3*isq!tpr> oi aXdiaaoq »^"Solo79di ,zt dl .bvsvujS- i3. C| V*i r rjyto
ddgi-aw Isadoc add aattd- art} jj^tc^a .Isiiil add- nx bsniftddo •8«oxd^^bM--' , '*J:toubwq
dixv, , . t fcT>dei.jqo lo -tf.iru>l«;R arid od 'ildxl ffivra ■ df on ItidB. *»* baoobo^q eniB-im lo
vtlittefcii Xlsno b^BBd xidsnttreaaq- v^9d/:I addnoir iX sojob babivctq z&iuaitl noliont'ciq
-qo ad* 'od nwofijl •.•>d ^io.hes'oq bdifoo ribtdvr i>-: oi/bcrro Yd-x-t^Jaap gnxb^^s^'f oxdcrintolnc
■^Tsdfoidq&a' ? 9-idBT nx n.foris ei& en ca ii r.qnioo- rtocB-tol ''d.rn.cr i.^fr) B^ei^vJ; vioiT^e
*llb sdd t no8s98 %1$X add* lof • -.ctstdB aonyir^is'; va' anoseae ^X'brw-.-^ox edd iol
-ta^cdsiq O^JX 9rii -bns XjartJgt.^X 'add: tri bditoqat noXdot6p < iq ni e^ona-tal •
»dd ffoer-se 05?X --and -io^ .rd^'iia-'tavo jwadaienoo don bfta 'JXBijw.^egB^B -ydd no -anc-
.•edeitfa XXb • ei • ng i« 9<rbb ?dd lo #?b ttfie • f exd«Bdedire iioM-Ms •Baan-.tellib ^sinavB
add nx badioqaiTabnif a»w Bniexet Xa*nidfift ftox to-wb-ow 05^1 .-add t ?3B7ovB »fcf no
oDsni? 9rft • .icatro* X^X -dt dd ^ 'ttoa i^teqmoo- • -ni *fl9t> nxq .f. ajuoa \d T-^nua :X««fl-0^?I
ffsdd ax da^tainx lo dosl «ihrid»««rl a. .drt&o TWqf S dwods ej? ^X -rol a-ifr^n auoa
ia^ "to tdidnBf^>--add Id dn*ibtt$tifsbni don a/sw-xsvura X^nll- O^PX odd ni gwidaocpn 2bnn
ssawsfTf 5 £>dd no- t dBdd edBoifotti ?.9£dst af nwoda ed«b odT .dihxr srii ito bsoxrfwm Bstia
26
TABLE 8
Comparison of Production of Natural Raisins Reported
for Identical Units in Season Final and Subsequent
Season Preharvest Surveys, 19U9 and 1950 Seasons
Reference
strata
Reioorted production of
natural raisins per unit
Final as
per cent of
preharvest
Number
of units
Current j Subsequent
final ! preharvest
tons
19U9 season^/
I
if 0
96.7
II
100
62.1
61.1
101.6
III
111.2
112. U
98.9
IV
h
h 83. 5
U79.9
100.8
AT 1W
22. h
22.9
97.8
19^0 season
I
502
!
8.9
9.7
91.8
II
115
35.3
37.8
93. a
III
60
57. U
63.6
90.3
IV
8
181- 2
193-3
93.7
All*/
1
11.6
j
12.6
02.I
a/ Sample units located in Fresno, Kings, Madera, and Tulare counties.
b/ Weighted averages of stratum means; weights used are numbers of raisin
~ type grape units within the four acreage strata in seven surveyed
counties.
TABLE 9
Average Differences in Production Reports and Variances of
These Differences Related to Quantity of
Natural Raisins Produced, 1950 Season
Reoorted
production of ,
natural raisins-'
Number
of units
Mean difference
in production
reports^/
Variance of
differences
tons
tons per unit
0
351
+ 0.3
7.1
0.1- 9.9
73
- 0.2
' 3.U
10 - 19.9
66
- 0.3
23.9
20 - 29.9
S 58-
- 2.0
39.7
30 - 39.9
hh
- 3.7
93- b
U0 - U9.9
21
- 6.1
11U.1
50 - 69.9
21
-10.6
271*. 7
70 - 99.9
15
+ 2.9
66.3
100 -199.9
26
-10.7
735-9
200 -699.9
10
i . ■ — —
-2U.9
2,2U0.1
a/ Based on reports in 1951 pretarvest survey.
b/ Production of natural raisins reported in 1950 final survey
~~ minus production for identical units as reported in the 1951
preharvest survey.
.7s
1
■
S.O V,
■
•" P 0 -
FY
1
- 01
O.S - . . j
v> . *?S ~ OS
■
I Ju *i 1.1 XX " J
1 1
• •
*.ox-
i is
- 05
I >
V.OX-
: ^ s . ]
9 .J^^X— oox
J. -Uiii^i •
j
r
; § COS
• )£9VTi/e j-asvtwisrr'- I<??I isi sitoc^i no beesg
28.
underreporting was greater in absolute amount for units producing substantial
quantities of raisins than for smaller units.
The standard of comparison used above is admittedly not perfect since re-
sponses of operators regarding preceding year's production are subject to memory
bias and distortion; actual crop weights as shown, for example, on weight tickets
would provide more satisfactory check data. Nevertheless, these comparisons are
fairly indicative of a major source of error to which estimates of natural raisin
production prepared at the end of the production (but not the marketing period)
are liable. Such errors cannot be controlled by increasing the size of the sample.
Given that raisin production estimates have to be prepared late in September or
early in October, it would appear that the only possibility of controlling effec-
tively response errors lies in the introduction of some objective measurements such
as weights and counts of raisin containers as an integral part of the measure-
ment procedure. This will increase substantially the cost of the final survey.
Only further investigation can determine whether a final survey procedure based
wholly or in part on objective measurements is at all feasible under a realistic
budget.
Efficiency of Stratification . It is generally agreed that a listing intended
to be an exhaustive census of a large class of elements can seldom be entirely
complete, entirely accurate, and wholly up to date. In using an existing list as
a frame from which to sanrole a definite hazard must be accepted of not being able
to sample elements which are in the population intended to be sampled but not in
the frame and of having to sample and include in various counts and expansion
factors fictitious elements still in the listing, but no longer in the population.
Yet, if a listing exists which is reasonably complete and accurate, sampling di-
rectly from such a list offers advantages which frequently more than compensate
for the difficulties that may be encountered. In agriculture, a listing of ele-
ments (if it exists) is ordinarily more than just a bare enumeration of units.
The listing provides some information concerning the population to be sampled,
data which might enable an efficient use of devices such as stratification to re-
duce substantially the sampling variability of estimates. It should be added that,
if the accuracy of expansion factors as derived from the listing is seriously in
doubt, estimates may sometimes be employed which depend less directly on these
factors.
The listing of grape units, revised annually, which served as the frame for
the raisin production surveys, provided for each unit the acreage in grapes by
varieties. In particular, for raisin-type grapes, the listing indicated for each
unit the bearing acreage of Thompson Seedless, Muscat, and Sultana varieties. It
.65
Jsxinsiadcra ^ftiDubo'iq s.iltiu tol irurocffi aicloadr n j -jaia'vrg eew 3nii , rri|$'i*TPbnn
> ' : ;: . .eiim; *9XXxunB *iol nsrii aniaxs'T'lo aaxtxinst'c
~9t aonXs d^ttoq inn v.X'Sai+xmbs ax avods basxi nozrrzwnoo lo trcxr.bnsia axfT
yicmam ox- ioatrit/a a-xs ncl-int/bom^e ■asay tjnxb'aoaiq an/Msas-* a'roisiaqo lo aaanoq'a
ajatfoxi irfgJrew no ,9£qmsx9 lol ,nVrorf-e a;= airi^isw qoto iewto* jnoliioie ib bns asid
&1a enoarrsqroo oayrfi tHeaWii^vaV .aisb- 3?oarfa yjoioslaiisa «toh sb rvoiq- hXuow
fixaxisi Csnfi.sn lo eotemitea 'Haifa c-.t ions lo a-vinoa rtotam p. lo ov#j\*>xbni yiVfel
(faoiieq ^n.tx r^siB arfi ion iud) noxioabo-cq arid- lo fens erii is" hsiuqma notiotrbotq
n r qmsc grfi lo ssxe arfi gnxasstonx yd bar X<->tinco ed ionnsn tsia»rw doa8 .aldsxi sis
to t»dm^cZ ax baisqoiq ad oi evsri .eaisisiiae xioiioafooic nxexsi isdi navxO
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29.
will be recalled that bearing acreage of the three major raisin grape varieties
was used as a stratifying variable. One would expect that stratification on the
basis of bearing acreage would be efficient for the estimation of total production
of raisin-type grapes, but not necessarily so for the estimation of raisin production.
As is evident from Table 3, many units (an estimated hO per cent of units in 1951)
do not produce raisins, and for units producing raisins, acreage harvested for
raisins is far from perfectly correlated with total bearing acreage of raisin-type
grapes .
Some indication of the efficiency of stratification may be obtained by com-
oaring the (estimated) sampling variance cf estimates provided by the stratified
design with analogous (estimated) variance appropriate for unrestricted sampling.
It is easily shown that an unbiased estimate of the over-all variance derived from
data of a stratified sample is given by
h N n
in which
|
, h a
h
and the other symbols are as defined previously. A measure of relative precision
of stratified as compared with unrestricted sampling is given for linear expansion
by the ratio
tj M(N - n)/n S a^U" 1 - £j
which also supplies an approximate indication of the factor by which sample size
must be increased if unrestricted sampling is to provide estimates matching the
sampling accuracy of stratified data.
This factor is shown in the tabulation below for four linear expansions based
on the 1^1 final survey. As w a s expected, the efficiency of stratification ap-
pears to be considerably greater for items pertaining to grapes than to raisins.
Nevertheless, gains from stratification for all linear expansions are consider-
able. The smallest gain is obtained in the estimation of production of natural
raisins. Even in this case, calculations show that an unrestrictedly drawn sample
of some 1,323 units would be needed to match the sampling accuracy of a stratified
sample of 7?8 units. These remarks apply only to linear expansions. For other
types of estimates shown in Table h, gains from stratification, if any, are likely
to be more moderate.
Km or
0-7
30.
Efficiency of Stratification (Reference Strata I-IIl)
Linear Expansions, 19!>1 Final Survey
i
Estimated sampling variance^/
Rplative
Item
Unrestricted
Stratified
precision
Bearing acreage
8U.1
20.6
U.i
Acreage harvested for
natural raisins
37.1
19.2
1.9
Production of raisin-
type grapes
5630
1823
3.1
Production of natural
raisins
1U2.7
82.9
1.7
_
a/ Entries should be multiplied by 10° to obtain actual magnitudes.
•
A
31.
APPENDIX
Schedules of the 1951 Raisin Production Surveys
I. Preharvest Survey Schedule
California Crop and Livestock Reporting Service No.
P. 0. Box 1258, Sacramento 6, Calif.
1951 Raisin Grape Preharvest Survey
(Name of Operator) (Street, Route, Box) (City) (County) (Note Corrections)
Phone No.
Location of Vineyard Unit: Sec. : Twp. : Range : By Roads ;
(Correct if necessary)
Thompson Muscat Sultana
1. Bearing acres of raisin grapes in unit in
1950 Acres Acres Acres
2. Acres harvested for raisins in 1950 Acres Acres Acres
3. Tons of natural raisins Droduced in 1950 from Dry Dry Dry
unit tons tons tons
h. Additional bleached tons produced in 1950 from
unit " " "
5- Bearing acres of raisin grapes in unit,
1951 Acres Acres Acres
6. As of today how many of the above bearing acres do
you intend to harvest for raisins this year? . . . Acres Acres Acres
7. Estimated total oroduction of grapes on this
unit:
Fr. Fr. Fr.
a) in fresh tons in 1951 » • tons tons tons
b) in fresh tons in 1950 n ■ "
8. Has harvest of this unit been completed for this season or have all the vines
been girdled so that no raisins will be produced this year?
Interview made by Date: August , 1951
(Put comments on back)
301 vise
<Sf!
esioA^
891 oA
BOTO&
30 0<*
8910 A
erto#
- S'^fUS^
tii iinv ni 29CfBT:9 niaxBT to eeiofl an
.Q^VI ni: ani:s c8i iol baches v*£8
baoubotq eriod
J9ld IsfV
3910A B910A 2910 A
e^ioA BciioA esioA
32.
II. Wi thin-Season Surveys Schedule
Raisin Grape Production Survey-
September, 1951
Please answer the questions below only for the
vineyard unit you operate located in Range ,
Twp. and Section
on which there are the following bearing acres of raisin
variety grapes:
Thompson S. , Muscat , Sultana
Your answers to the first four questions below
should relate to raisin grapes harvested to the close of
Please answer every question; enter "0" or "none"
where it applies.
Do not include in this report information about
other varieties of dried grapes.
(Report for each variety in
columns indicated)
Thompson S.j Muscat
Sultana
1. Total acres of raisin
graoes harvested
through above date for
raisins, fresh ship-
ment, or crushing. . . acres
acres
acres
2. Acres of grapes
harvested for natural
raisi ns only this sea-
son through above
acres
acres
3. Total number of trays
harvested through
trays
trays
U. Estimated number of
tons of natural rai-
sins expected from
graces harvested
through above date. . . dry tons
dry tons
dry tons
£. Total acres of raisin
grapes you expect to
harvest for all types
of raisins this sea-
acres
acres
Reported by>
Pat'et" Septembe r 1951
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- 1 noxio92 bne .qwT
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^uocfe noxignrao'inx tfioqoa aid* ni sbvlant Son crt
1
, 8910$ , ] x
IfillfoSIi Tot b viS9V16r{
-bob aid.t ^Ino efiraisi
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by**x^ lo 19'ImLT! Lsd-oT
i
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•
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I a9T0B
III. Final Survey Schedule
California Crop and Livestock Reporting Service
P. 0. Box 1258, Sacramento, California
Final Raisin Grape Production Survey
September, 1951
Name:
Phone :
Address !
Location:
Please obtain answer to the questions below only
for the vineyard unit located in Range: ,
Twp: Sect: on which there are the
following bearing acres of raisin variety grapes:
Thompson S.
Muscat
Sultana
Complete every question; enter "0" or "none" where
it applies. Do not include in this report information
about other varieties of dried grapes.
(Report for each variety in
columns indicated)
Acres of grapes har-
vested for raisins
during entire 195>1
season
Thompson S.I Muscat Sultana
acres
acres
acres
Estimated number of
tons of natural rai-
sins produced in 1951
from the above acres
harvested dry tons
How many additional
tons df any) of
bleached raisins were
made this season from
above acreages har-
vested dry tons
Please estimate the
total production of
grapes on this unit
in 1951, in fresh
tons
dry tons
dry tons
dry tons
fr. tons fr. tons
drv tons
fr. tons
Enumerator:
Date : October
, 1951
£»0