College and Research Libraries R I C H A R D W . T R U E S W E L L Some Circulation Data from a Research Library This article contains the results of an analysis of the circulation for all monographs from a research library during a six-month period. The data have been tabulated and plotted to show the percentages of users accounting for the corresponding circulation. J R . ECORDS W E R E maintained during a six- month period of the names of the users and the number of books borrowed for all monographs circulating from the AF Cambridge research library. These da- ta were then tabulated by user and ranked according to the number of mon- ographs the user borrowed. The data were then grouped and tabulated as shown in Table 1. The headings should be self-explana- tory, but some comment will be made about the entries in order to avoid mis- interpretation by the reader. Line 1 of Table 1 represents eight users who bor- rowed seventy or more books each, or a total of 827 monographs. These 827 monographs represented 9.2 per cent of the total circulation for the six-months study period, and the eight users rep- resented .95 per cent of the users. Line 2 and the remaining lines of Table 1 represent cumulative data. For example, six people borrowed from sixty to sixty- nine monographs each. This resulted in Dr. Trueswell is Head of the Department of Industrial Engineering, School of Engi- eering, University of Massachusetts. This article was prepared as a part of the authors USAF active duty training through the Of- fice of Aerospace Research with assignment at the AF Cambridge Research Laboratory Research Library. This data was provided through the cooperation of Ole V. Groos, Director of the AFCRL Research Library. a total of fourteen people (having the largest circulation needs) who borrowed sixty or more books each or a total of 1,217 monographs. The cumulative data in columns 5 and 6 of Table 1 have been plotted in Figure 1 to give a "user characteristic curve." This curve is a plot of the per- centage of monographs circulated versus the percentage of users accounting for the circulation. Figure 1 shows that only 12.5 per cent of the number of active borrowers ac- counted for 50 per cent of the circula- tion. Similarly, 50 per cent of the active borrowers accounted for 90 per cent of the circulation. The AF Cambridge research library contains approximately one hundred and twenty-five thousand volumes, primarily in the physical and environmental sciences area. It provides services to the approximately one thousand scientists, engineers, and staff members of the AF Cambridge research laboratory located at L. G. Hanscom Field in Redford, Massachusetts. The laboratory is a part of the Air Force Office of Aerospace Re- search. It is interesting to note that 835 individuals out of a possible one thousand borrowed at least one monograph during the period of study. C O N C L U S I O N S The results are presented primarily for informational purposes. The salient point / 493 494 / College