key: cord-0845343-vj85zdzd
authors: Tanriverdi, Gokhan; Bakir, Mahmut; Merkert, Rico
title: What can we learn from the JATM literature for the future of aviation post Covid-19? - A bibliometric and visualization analysis()
date: 2020-08-28
journal: J Air Transp Manag
DOI: 10.1016/j.jairtraman.2020.101916
sha: e09e15aba7c2c5d7f520613a121ec23154ca41af
doc_id: 845343
cord_uid: vj85zdzd

This paper aims to draw lessons from retrospectively evaluating the evolution of the air transport discipline right up to the COVID-19 outbreak through the Journal of Air Transport Management (JATM), the main scholarly air transportation journal globally. As such, this study deploys a comprehensive bibliometric analysis and graphical mapping of the JATM knowledge body through CiteSpace visualization of 1483 JATM papers from 2001 to 2019. Our results suggest that while the industry has experienced pandemics and economic crises in the past, both were not dominant in influencing JATM literature neither in frequency nor in impact. That said, recovery, crisis and disruption are important key words in JATM papers not just in regard to safety and economic crisis management but increasingly also related to health concerns with recent key papers published in the pandemic and recovery management context which may have helped the industry dealing with the current crisis as well as current JATM papers on this topic assisting with preparing for a transitioning out of COVID-19 world.

Since the US Airline Deregulation Act in 1978, the global air transport industry has experienced a 20 remarkable growth and transformation process. Ever increasing demand but also changing ecosystems 21 have led to the emergence of new business models such as low-cost airlines (Ko, 2016) resulting in the 22 average airline becoming more diversified with many full service carriers having low-cost carriers as 23 part of their holding or corporate portfolio (Pearson and Merkert, 2014) . While the aviation industry 24 has since its inception been exposed to endogenous risks and volatilities of both demand and costs (i.e. 25 fuel costs; Merkert and Swidan, 2019) it has always been able to restructure, show resilience and 26 bounce back sharply even from crises and disasters such as the Oil Crisis, the Gulf War, the Global 27 Financial Crisis, the 9/11 terrorist attacks, the Severe Acute Respiratory Syndrome (SARS), Swine Flu 28 (H1N1) and Middle East respiratory syndrome (MERS) (Chung, 2015 ; ICAO, 2020). As such, the 29 industry kept growing and operated as many as 38 million scheduled commercial flights and carried 30 4.3 billion passengers in 2018 (Industry High Level Group, 2019), supporting 65.5 million jobs 31 globally, including 10.5 million airport and airline staff, and $2.7 trillion in world economic activity in 32 2019 (ACI and IATA, 2020). However, since early 2020, the aviation industry is facing its perhaps 33 greatest challenge ever as it is struggling with the COVID-19 pandemic (IATA, 2020a), which 34 resulted in closed borders and many airlines not only coming to a standstill, with hibernating of up to 35 95% of their fleets, but some even going into voluntary administration (e.g. Virgin Australia or 36 are used in this study. Among these, the number of studies, the number of citations, average citation 145 per study, h-index are the primary metrics deployed in our analysis. In this context, the number of 146 studies denotes productivity while the number of citations indicates the journal's influence (Donthu et 147 al., 2020) . Besides, per-citation and h-index are important indicators of influence. The h-index, which 148 is considered to be a robust influence metric, shows the number of h studies in a journal that exceeds h 149 citations . Also, the publication development of JATM is analyzed using citation 150 thresholds (Cancino et al., 2017) . Apart from these, the most cited studies, basic statistics about 151 leading institutions, authors and countries, and frequently used keywords are also preferred (Modak et 152 al., 2019) and hence deployed in this paper. 153

Retrospective evaluations are usually based on the integration of two approaches: evaluative and 155 relational techniques. While evaluative techniques focus on productivity and influence metrics 156 described in the previous section, relational techniques visualize existing relationships and provide 157 information about past and present trends (Guzeller and Celiker, 2019) . Graphical mapping called 158 relational techniques aims to provide deeper insight into the intellectual structure of a particular field 159 or journal . In this study, graphical mapping is developed using CiteSpace. 160

CiteSpace, developed by Chen (2006) , is a software that allows visualization of knowledge areas, 161 defining past and present trends, and categorizing the information in narrower clusters (Zheng et al., 162 2017) . Although there are many other software packages (i.e. VOSviewer, BibExcel, HistCite, etc.), 163

CiteSpace is preferred in this study because it allows extra analysis such as burst detection (Li et al., 164 2017) . 165

Graphical mapping analysis includes co-citation (authors, documents, and journals co-citation), co-166 author analysis (authors/countries/institutions co-occurrence) and co-word analysis (keyword 167 occurrence). Co-citation occurs when two publications cite to the same third publication. The co-168 authorship indicator illustrates collaboration networks, in other words, the extent to which the units are 169 connected (Mulet-Forteza et al., 2018). Co-word analysis is also used to identify and measure the most 170 frequent keywords in publications. By doing so, the intellectual structure of the relevant literature can 171 be explained and trends can be identified (Donthu et al., 2020; Guzeller and Celiker, 2019) . Also, we 172 deploy burst detection and cluster analysis in this study. Burst detection shows the presence of specific 173 keywords, authors, and institutions that exceed the predefined thresholds in a certain period. It can be 174 concluded that the items with strong bursts have great domination in a certain period or have become 175 an important (past/current) trend (Guzeller and Celiker, 2019; Zhou et al., 2019) . Finally, the cluster 176 analysis provided through CiteSpace analysis helps to identify similar research topics according to the 177 related keywords. In this analysis, each cluster represents the basic research topics that make up the 178 knowledge body in the journal. By doing so, the goodness-of-fit value is measured by the silhouette 179 score ranging between -1 and +1 (Li et al., 2017) . Accordingly, higher silhouette scores show the 180 J o u r n a l P r e -p r o o f homogeneity between the items. The cluster labels formed as a result of the analysis depend on the 181 keywords. In this context, the log-likelihood ratio (LLR) value compares the probability of having a 182 keyword in one cluster compared to the probability of having the same keyword in another cluster and 183 evaluates the goodness-of-fit of each cluster in this way. Thus, the homogeneity of the labels is met 184 . Finally, the modularity Q value, ranging between 0 and 1, indicates that the 185 relationship increases between clusters as it approaches 1. Generally speaking, Modularity Q values 186 between 0.4-0.8 are acceptable (Li et al., 2017) . 187

The bibliometric data collection process 188

In this study, the evolution of the air transport management field using JATM literature until 189 COVID-19 (by end of 2019) is presented with a comprehensive bibliometric analysis. The JATM is a 190 scholarly journal that publishes original articles in areas such as economics, management and policy 191 related to the air transport industry. JATM was first published in 1994 by While the journal's first editor was Rigas Doganis, Sveinn Vidar Gudmundsson and Rico Merkert 193 currently lead the journal as Editors-in-Chief. JATM offers its readers access to independent, original 194 and double blind peer-reviewed studies in major areas such as policy/regulation/law, strategy, (SJR) reported that the CiteScore of JATM is 3.27, and JATM ranked 27th in the "Transportation" 200 category. While this rank does not seem high, it is worth noting that JATM is a niche market journal 201 with its focus on one mode of transport that is aviation only. What is more, over the last five years the 202 Citescore has gone up from 1.31 in 2014 to a predicted score of 3.60 in 2019, which evidences a 203 strong trajectory of JATM in gaining in importance and impact in the wider academic literature. 204

The bibliometric material used in our study was retrieved from the WoS database. found. As can be seen in Table 1 , the documents are mostly composed of articles (n = 1401, 94.4%). 223

This percentage also includes proceedings papers. Other bibliographic material are editorials (n=49, 224 3.3%), book reviews (n=25, 1.7%), reviews (n=4, 0.3%), biographical items (n=2, 0.1%) and 225 corrections (n=2, 0.1%). 226 year was recorded as 3523. Table 2 also reveals that studies with more than 100 citations account for 259 only 1.21% of all studies, and more than half of the studies received at least 5 citations. When we 260 examine the cited studies, it is evident that 88.8% of the publications received at least one citation, 261 which shows that JATM generally hosts publications that are consulted and cited in the field and that 262 increasingly so. As such, while considering the citation thresholds, it should be noted that the studies 263 

Another aspect worth examining in regard to JATM is the most cited papers. Table 3 performance, and passenger demand, it is evident that safety and service quality issues stand out as the 293 most influential topics within the air transport management area. Particularly the focus on safety is 294 interesting to a COVID-19 context where safety and particular health concerns has become even more 295 paramount. That said, the fact that the most recent study in the top 20 was published in 2011 which 296 indicates that time is needed for the contribution of more recent publications to become visible. 297 

Valuable perspective can also be obtained from the analysis of the most productive institutions and 301 countries in JATM, as summarized in Table 4 . Cranfield University ranks first in terms of the total 302 number of studies and total citations, followed by University of British Columbia and Loughborough 303

University. Considering the average number of citations per study, there are notable differences in the 304 ranking as the University of California System is ranked first with an average of 25.32 citations, 305 followed by National Cheng Kung University with 20.50 citations and the University of Westminster 306 with 19.10 citations. Generally speaking, leading institutions in terms of institutional ranking are 307 located in Anglophone countries. Besides, the most productive countries are the US, England and 308

Taiwan. Countries such as Germany, Australia and China are also well represented in these rankings. 309

Considering the average number of citations per study, which is an indicator of influence, it is evident 310 that the Netherlands is first with 18.30 citations, followed by Portugal with 16.88 and England with 311 16.28 cites per paper, respectively. 312 Table 4 

Source: Publication data based on WOS data and population data retrieved from Worldbank.

J o u r n a l P r e -p r o o f

Another important issue in a bibliometric analysis is author productivity. Table 5 lists the 334 productive authors in JATM with Niemeier HM ranking first in terms of the total number of papers 335 (22) followed by Oum TH (21) and Zhang AM (16). Considering influence as measured by the total 336 number of citations and average citations per study, Table 5 is an active scientific community that takes thought leadership. In this regard, scientific conferences 358 are very important, which enable researchers to communicate their findings and come together. 

In this section, authors and journals citing JATM are analyzed. Table 7 we observed that these journals are mostly in the field of transportation, and in this respect; JATM has 378 made a significant contribution to the related literature. 379 

To deepen the insights of the bibliometric results, in this section, a graphical mapping of the 384 publications in JATM is developed. In doing so, we first examine the document co-citation network. 385

As defined earlier, co-citation occurs when two publications receive a citation by the third 387 publication from JATM. Based on our CiteSpace analysis, the co-citation network of 1483 388 publications is illustrated in Figure 6 suggesting that many different types of studies are cited in JATM 389 publications. In this regard, the most cited study in JATM is "The impact of strategic management and 390 fleet planning on airline efficiency-A random-effects Tobit model based on DEA efficiency scores" (n 391 = 20) published by Merkert and Hensher (2011) . This is followed by "A non-parametric efficiency 392 measure incorporating perceived airline service levels and profitability" (n=19) by Merkert and 393 Pearson (2015) and "The growth limits of the low-cost carrier model" (n=19) by de Wit and Zuidberg 394 (2012). In addition to the co-citation analysis, Figure 6 also presents clusters of the knowledge body 395 based on the cited documents. Note that the colorings in stripes on top of the map reflect the citation 396 dates of the studies. According to Figure 6 , a wide range of clusters are identified, from low-cost 397 carriers (#0) to small regional airport sustainability (#2) and airline service quality (#3). 398 399 Fig. 6 : Document co-citation analysis 400 Table 8 , moreover, details seven major clusters using cluster labels and mean silhouette values. 401

Considering that the prominent clusters give clues about trend topics, it can be concluded that the 402 hottest topics in JATM are low-cost carrier and airline service quality, the former going to be hit 403 hardest by COVID-19 and both likely to be heavily researched in that context. Finally, the modularity 404 Q value of the figure is 0.7727, indicating that there is a high relationship between clusters. The mean 405 silhouette value is also 0.4542, indicating medium level homogeneity. 406 Table 10 and Table 11 provide more detailed institution and country-based citation burst results. 14 438 bursts were detected for both categories. subset of data both separately and as a whole through the Citespace and while none of these SI words 473 made it into the most frequently or centrality words, as shown in columns 1 and 2 in Table 12 , it is 474 evident that Recovery, Crisis and Disruption are of importance to the discussion in the JATM 475 literature, as shown in column 3 of Table 12 , and are in fact not far of the top ranking. As safety is at 476 the very heart of the aviation industry, it was expected to see crisis management and recovery in 477 relation to aircraft accidents (Chang et al., 2018) in that list. A more in-depth analysis of the relevant 478 papers picked up by the SI words has revealed that a number of these were not only recent but also 479 related to recovery from demand disruptions (e.g. Delgado et al., 2020) and economic crisis (Barros, 480 2008 ) and importantly also to pandemic management research. Notably, Gold The citation burst results shown in Table 13 strong bursts, thus these words can be seen as emerging trends. What is missing from a COVID-19 498 perspective is bursts around our SI words such as pandemic or recovery and even crisis did not 499 produce a burst in past years. There is of course any chance that the present JATM special issue will 500 produce such a burst in the future. Content analysis showing the response of European carriers to 501 COVID-19 ranging from innovation to exit (Albers and Rundshagen, 2020), remarks on the 502 aeropolitics in a post-COVID-19 world (Macilree and Duval, 2020), as well as findings showing that 503 the attitudes of ageing passengers will matter relatively more in such a world (Graham et al., 2020) 504 which will and in many jurisdiction already has led to innovations such as self-service technology in 505 airport. As such there appears evidence that JATM bursts will emerge around both technology and 506 also process innovation such as innovative security control lane operations during the COVID-19 507 epidemic. Even before the special issue, recent JATM literature has picked up the COVID-19 theme 508 such as Nikolaou and Dimitriou (2020) who have deployed epidemiological models to evaluate the 509 In terms of core subject areas, our analysis has shown that JATM has been an important source for 527 leading journals in many different areas such as safety, transport, operational research, sustainability 528 and tourism. In regard to the journal's research productivity the U.S. is by far the leading country but 529

China's contribution to the JATM literature has gradually increased over the analysed period. 530

Considering collaboration networks, we found that international and even intercontinental 531 collaborations are common in JATM. Mainstream topics in JATM are found to be focused on the 532 airports, airline alliances and low-cost airlines. While during the analyzed period of 2001-2019 the 533 aviation industry witnessed various infectious diseases and crises (Chung, 2015) , JATM papers 534 focusing on these disasters were less prominent in the results of our bibliometric analysis than initially 535 expected. Considering the most frequently used words as a piece of evidence, words associated with 536 the topic of this special issue (i.e. COVID-19) and in particular recovery, crisis, disruption were 537 however close to the top key words of JATM publications. What is more, we found some recent key 538 papers on pandemic management, prevention and recovery. The latter has a long tradition in JATM, 539 unsurprisingly related to safety and aircraft accidents but also economics crisis and recently epidemic 540 crisis. That disease and health words were not featuring in the top 15 of frequently used words is 541 understandable as the JATM literature is quite large and also because previous outbreaks were not as 542 catastrophic as COVID-19 on a global scale. However, it is anticipated that this pandemic and health 543 will attract more attention in future studies, not least through this JATM special issue, and the 544 unprecedented impact of COVID-19 on the global air transport industry. 545

Although we are confident that our bibliometric analysis presents a comprehensive and rigorous 546 evaluation, there are some limitations. First, this study covers the period of 2001-2019. While that is 547 the entire population of JATM indexed papers in the WoS database hence impossible to include more 548 papers, we note that recent publications continue to evolve including gray publications at conferences 549 etc. That said, this is in our context less a problem than normally as many conferences have been 550 cancelled due to COVID-19. Secondly, our bibliometric analysis has an inherent limitation as the full 551 counting approach was used. If there are many authors from the same country or institution, the 552 number of frequencies is multiplied by the number of authors which provides an advantage for multi- Overall we are confident that our paper presents not only a general overview of the journal but also 564 provides reference to COVID-19 and research related to pandemics and crisis management in the 565 aviation context, which can offer managers key clues for possible decision-making situations in the 566 future. In future studies, a broader perspective can be provided to readers using a wide range of 567 bibliographic metrics. In addition, we recommend to repeat our study in five years to illustrate to what 568 extent air transport has been discussed as a reason for spreading outbreaks around the world but 569 importantly also a key element of medical and essential good logistics but also repatriation flights 570 during outbreaks. In this context, the anticipated increase of the studies focusing on COVID-19 from 571 various perspectives will help clarify the relationship between air transport and management/recovery 572 of/from pandemics. This will also enable future studies to reveal whether the industry has learned from 573 the JATM in terms of preparing for a potential future pandemics or further waves of COVID-19. Thus, 574 more valuable insights can be offered in the future using bibliometric analysis on a continued basis. 575 576

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Six Decades of The Accounting Review: A Summary of Author and 653 Institutional Contributors

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COVID-19 Dashboard by the Center for Systems Science and 666

Engineering (CSSE) [WWW Document

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Hospitality and tourism research rankings 725 by author, university, and country using six major journals: The first decade of the new 726 millennium

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Scholarly influence in the 730 field of management: A bibliometric analysis of the determinants of University and author 731 impact in the management literature in the past quarter century

Knowledge structure in international marketing: A multi-method 734 bibliometric analysis

Systematic literature review on air transport and 737 tourism: Analysis from 54 journals during the period

An early assessment of the impact of 741 COVID-19 on air transport: Just another crisis or the end of aviation as we know it?

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A bibliometric 746 analysis on trends and characters of carbon emissions from transport sector

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Coronavirus pandemic and tourism: Dynamic stochastic general 757 equilibrium modeling of infectious disease outbreak

Cross-institutional collaboration networks in tourism and hospitality 760 research

Evaluation of sustainable transport research in 762 2000-2019

764 Bibliometrics study on the Journal of American College Health: 1994e2014

Mapping knowledge domain of "transport": A bibliometric 767 study of its status quo and emerging trends

Analyze the JATM literature in an innovative manner through bibliometric analysis method

• Analyze 1483 JATM papers from 2001 to Covid-19 outbreak

• Conduct graphical mapping analysis through the CiteSpace software

• Based on the WoS database, identify publication/citation structures, leading powerhouses/authors, etc

This paper is expected to motivate researchers to publish more Covid-19 paper in the aviation management field