Ranking of Sustainability Journals Using the Author Affiliation Index and Comparison to Other Journal Metrics

An important component in evaluating research productivity is the quality of the academic journal. For this reason, the objective of this paper is to analyze the Author Affiliation Index (AAI) in sustainability field journals as a preliminary study to offer some insights into quality rating of journals in this chosen discipline. The AAI of a journal is defined as the percentage of the journal’s articles published by authors affiliated with a base set of high-quality academic universities or institutions. We conducted an evaluation of the top 50 journals in environmental studies indexed in the category Social Science in the Web of Science (WOS) database in 2018 and the top-notch 50 universities worldwide with master or postgraduate programs in the disciplines of management and sustainability studies. The results obtained demonstrate that there is a low AAI score on average in the sustainability field compared with other disciplines and the potential reason for such low scoring is probably caused by the high number of co-authors collaborating in environmental studies related journals. Although there is no agreement reached in terms of journal ratings by AAIs and other citation and survey-based measures, we can confirm certain elite affiliations effect which leading sustainability journals have higher concentrations of authors who are affiliated with elite institutions, however, such elite affiliation effect is on average much lower compared with other disciplines as finance, accounting or transportation, etc.


Introduction
Academic journals have been studied repeatedly to determine the best in terms of quality. Various statistical tools such as regression analysis [1], stochastic dominance analysis [2], structural equation models [3] or correlation coefficients [4,5] have been applied in the literature. Different research has been carried out using more descriptive statistical techniques, such as cross-tabulation techniques [6], mapping techniques and metrics [7]. Some other work is carried out by adopting previously defined indicators as databases of doctoral theses on accounting [8] or selecting indicators such as institutions that have won Nobel Prizes and Fields Medals [9].
Moreover, there are several studies that have analyzed patterns in publications between journals and the author affiliations. Some examples related to this type of analysis can be seen in the field of environmental sciences [10,11], medicine [12,13], information sciences [14,15], management [16], engineering sciences [17], and biological sciences [18].
Accordingly, the purpose of this study is to analyze through the Author Affiliation Index (AAI) a set of journals, in this case the fifty most prestigious journals, that mainly address issues related to of journals provided by the AAI method with other ranking criteria, such as Web of Science (WOS), Scopus and Chartered Association of Business Schools (ABS), so as to display the difference in ranking results of AAI with other citation or survey-based rating measures.
The rest of the paper is organized as follows. Section 2 describes the methodology and data. Section 3 presents the empirical results and discussion. Conclusions are presented in the last section.

Formula
The original Author Affiliation Index (AAI) formula was set by Harless and Reilly [32] aiming to have an optional ranking for journal quality. Gorman and Kanet [23] applied the AAI in evaluating operations management journals using the following calculation: where AAI j measures the Author Affiliation Index for journal j; x i is the number of authors from a set of peer group institutions (x) in article i; y i is the number of US academic authors in article i not from the peer group institution set. Moreover, n is the total number of authors in article i and m represents the sample size drawn from each journal j.
As commented by Chen and Huang [21], bias may arise from this formula of calculation, as bias regarding non-US academics and non-academics is inherent for this way of application. Therefore, we follow Chen and Huang [21] and redefine the dataset (x + y) as all authors for article i not taking into account their affiliations (non-academics, US or non-US academics). Accordingly, x is defined to include all top-tier universities globally. Therefore, similarly as applied by Guthrie et al. [24], the AAI score is obtained by the sum of equivalent papers from top-notch universities in green, sustainability and environmental studies divided by the sum of equivalent papers by all authors, where equivalent papers indicate that each of the n authors of an article is given credit for 1/n. The calculation example of AAI applying our definition of (x + y) is displayed in Table 1.

Sample Construction
To conduct our study, our sample of journals comprises the 50 top journals of the Web of Science (WOS) database from Clarivate Analytics (previously the Intellectual Property and Science business of Thomson Reuters). Only Social Sciences Citation Index (SSCI) journals included in two categories were selected: "Environmental Studies" and "Green and Sustainability Science and Technology." All journals of these two selected categories (in SSCI) were merged together and ranked according to Journal Impact Factor provided by the WOS. In Table A1 (in Appendix A), it can be observed that some of the 50 top journals are also categorized in "Business," "Management," "Economics" or other disciplines. The complete list of journals is shown in Table A1 and is sorted according to the Journal Impact Factor obtained by the journal in 2018, which is the last available year by the WOS database.
Then we proceeded to obtain the institutional sample for our dataset x. For this purpose, we selected the best universities in the world related to the subject of sustainability linked to the scope of management and environmental studies. First, it is necessary to clarify that we are aware of the existence of many classifications and different rankings. Nevertheless, we selected the top global universities in environmental science studies ranked by QS Top University ratings [43] because it includes and considers a larger number of ranking criteria in order to elaborate the "Overall Score" obtained by a University. For example, criteria such as "Academic Reputation," "Employer Reputation," "H-index Citations," "Citations per papers," among others are taken into account.
Moreover, we decided to use this ranking provided by QS Top University because many academics have used this database to carry out their respective investigations. For example, engineering and technology subjects [44]; life sciences and medicine subjects: psychology subject [45]; communication and media studies subjects [46]; mathematics subject [47] and global subjects have also been analyzed [48][49][50].
For our research, we have selected from this database the 50 top universities worldwide in the disciplines of sustainability and environmental studies that have the best overall qualifications. Additionally, these universities have the most prestigious master or postgraduate studies worldwide in sustainability within the scope of management and most have business schools or faculties with a clear orientation to sustainability. Table 2 presents the 50 universities selected, as well as what they do in terms of teaching in management and sustainability. To obtain this data, the master or postgraduate programs of each of the selected universities were carefully examined. As shown in Table 2, almost all 50 top-notch universities have master or postgraduate studies in management education with specifications in corporate social responsibility (CSR) or sustainability. Some universities, such as the University of California, Berkeley, have MBA programs specialized in socially responsible investing and others offer broader programs, like the University of Leeds which offers a master in sustainability and business. Some of the universities on this list have specialized centers for teaching and research in management and sustainability. These include the Center for Responsible Business in Berkeley University, the Laboratory for Sustainable Business in MIT and the Cambridge Institute for Sustainability Leadership. We consider that it is very crucial that future corporate managers take into account factors and issues related to sustainability and environmental aspects for decision-making instead of only financial or business perspectives. We can see progress in this direction based on these management related master's degrees or MBA programs with specialization in sustainable development or modules in sustainability, CSR and business ethics offered by our sample of top 50 universities.

AAI Rankings
The authors used the top 50 journals in the categories of sustainability and environmental studies in social science journals and applied the calculations of the AAI formula as indicated previously. Dataset x includes the top 50 environmental science and sustainability journals ranked in SSCI by the WOS according to their impact factors. Dataset (x + y) contains all authors globally, academics or non-academics. Selected articles included research articles (theoretical and empirical) and research notes, but do not include book reviews, discussions or short comments, etc. The number of articles drawn from each journal m is set to 60 since previous literature [21][22][23][24] suggests that the AAI becomes stabilized when the size of m is bigger than 50. Therefore, sample articles were obtained for each journal from the latest issue of 2018 until 60 articles were selected. The majority of journals (37 out of 50) in the sample reach had 60 papers as the denominator with a coverage of only one year (2018). For the rest of the 13 journals, we examined from two to seven years' worth of articles to reach a denominator of 60 as shown in Table 3. As shown in Table 4, the AAI scores ranged from 0.019 to 0.276. Since Annual Review of Environment and Resources has the highest AAI at 0.276, this means that 27.6% of this journal's articles are authored by scholars from the top 50 ranking universities in our dataset. The mean of AAI for the 50 top ranking journals can be obtained as 0.126. This average of AAI according to our sample can be interpreted to mean that on average 12.6% of journal articles in the chosen field are authored by scholars from the top 50 top ranking universities as predefined in our dataset. The results of AAI scores in sustainability related studies are interesting compared with other AAI ranking studies. First, the AAI scores in the field of sustainability and environmental science in our peer group are significantly low (range from 0.019 to 0.276). Only eight journals out of 50 (16%) reached an AAI score greater than 0.200.
For example, a previous study in finance reveals that, on average, the AAIs are relatively higher with the top score being as high as 0.800 [21]. The range in the study of Gorman and Kanet's [23] regarding 23 operations management journals was 0.147 to 0.836 and 52% of journals in their sample had an AAI of 0.50 or higher. Compared with the results obtained by Guthrie et al. [24], the accounting field also yielded the highest AAI score at 0.795 and displayed higher AAIs on average. Research in transportation [33] followed a similar pattern and displayed the range of AAI scores from 0.090-0.670. To further study the reasons behind such a difference in AAI scores, it is observed that there are frequently many co-authors in the same publications in journals focused on the sustainability and environmental science subject. Actually, we found some academic papers signed by 94 authors (Ecosystem Services) or 88 authors (Nature Climate Change) in total, which significantly reduces the final AAI results. Table A2 (in Appendix A) displays the articles with author number count in the data set. We consider that these differences in terms of number of authors among distinctive disciplines occur because, in environmental studies, which is the case in many journals composed in our peer group, the work is carried out through research group projects where many researchers may work together in data collection and experiments, etc. However, in journals closely linked with scope of business or management, papers are usually collaborated among much smaller numbers of researchers.
As we can observe from the AAI ranking, most of the top ranking journals, such as the Review of Environmental Economics and Policy (2nd), Annual Review of Resources Economics (3rd) and Climate Policy (4th), are also within the economics or public administration categories. This result confirms the finding that journals closely linked to management, business or economics may have higher AAI scores due to the relatively fewer number of co-authors. In the case of the journal Annual Review of Environment and Resources (1st), it only has two articles with numerous authors (31 and 19) which increases the AAI scores.
The journal Nature Climate Change, which ranked first according to impact factor of the WOS, only occupied the 33rd position in the AAI's ranking criteria. Similarly, Global Environmental Change dropped from 2nd ranking position of WOS to 25th in AAIs rating. One possible explanation is that these two journals present a very high number of co-authors (88 and 39 respectively) in some articles, as shown in Table A2, which dramatically reduces the AAI scoring. AAI is very sensitive to the total number of authors and fewer number of co-authors may result in a higher number of AAI results. In addition, given our peer group of the selected top universities, these two journals are more targeted for publications in this sample.
It is also worth mentioning that some other journals, such as Environment and Planning A (50th position in the WOS), Marine Resource Economics (44th position in the WOS) and Annual Review of Resource Economics (41st position in the WOS), have dramatically higher rankings (10th, 9th and 3rd positions respectively) according to the AAI's method. Others also have higher rankings in AAIs since academics choose these journals to publish their research in environmental and social studies. For example, Sustainability went from 46th position in the WOS to 28th in AAI ranking; International Journal of Sustainable Transportation went from 47th position in the WOS to 21st in AAI ranking; and Climate and Development went from 48th position in the WOS to 24th in AAI ranking. Table 5 shows journals in our sample that belong to categories such as "Management" and other related categories with the highest number of authors in an article. Thus, the difference in the number of authors is observed (Table A2) between those journals closely linked with a business or management aspect and others only focused on environmental studies. The highest number of authors is 20 for business or management scope journals compared with 94 in Table A2 which marked a remarkable difference, although all journals in this study belong to the categories "Environmental Studies" and "Green and Sustainability Science and Technology" within the Social Sciences Citation Index (SSCI) of WOS. We would like to point out that the difference in terms of number of authors is notable comparing articles in Tables 5 and A2. We believe such a difference is relevant to the categories of journals: Environmental Study, Green and Sustainability Science and Technology or Management, Economics and Business related displines.

Comparison of AAI Ranking with Other Ranking Measures
We aimed to describe and examine the usefulness of AAI method in green, sustainability and environmental science journals to see if the top 50 ranked universities in these disciplines actually publish in the top 50 ranked journals of the same field. A comparison of AAI ranking with other ranking measures was carried out accordingly. We considered that such comparison of AAI score with other established measures (both of citation and survey based) was important, although the existing ranking measures do not set any peer group as the AAI method does.
Several criteria of ranking metrics were adopted as shown in Table 6. The Journal Impact Factor (JIF) from Web of Science "is a measure of the frequency with which the 'average article' in a journal has been cited in a particular year or period" [51]. As we can see from Table 6, the journal rankings have displayed a very different pattern comparing the AAI and JIF citation-based ranking. Among the top 10 journals ranked by JIF 2018, just two journals (Annual Review of Environment and Resources and Review of Environmental Economics and Policy) actually stay within the top 10 list according to AAI.
Two ranking metrics were drawn from Scopus. These were Scientific Journal Rankings (SJR) and Source Normalized Impact per Paper (SNIP). SJR metric is based on the idea that "all citations are not created equal" [52]. With SJR, the subject field, quality and reputation of the journal have a direct effect on the value of a citation. SNIP is an indicator that measures the average citation impact of the publications of a journal and corrects for differences in citation practices between scientific fields so as to provide more accuracy between field comparisons of citation impact [52]. As observed in Table 6, SJR and SNIP rankings display a relatively more similar pattern towards ranking. In general, the results of JIF, SJR and SNIP rankings have shown agreement on the first ranking journal, Nature Climate Change. To compare these two Scopus rankings with AAI, the results show a very disperse pattern. Only the journal Annual Review of Environment and Resources presents a very similar ranking among all four ranking methods.
The Academic Journal Guide (AJG) released by the Chartered Association of Business Schools [53] was also added for further comparison. The AJG is a guide to the range and quality of journals in which business and management researchers published their research. The AJG metric is based upon peer review and editorial and expert judgments following the evaluation of publications. The ratings are given as four categories from 1−4 in which a ranking of 4 indicates that journals represent those of distinction within the business and management field. In this case, we may see that some journals, such as Nature Climate Change which are not within the aforementioned fields, have not obtained any rating for AJG. There are 19 out of 50 journals rated by AJG in the economics, business and management fields. Upon the available ratings of journals based on the ABS list, the Environment and Planning A: Economy and Space journal ranked as the 10th in AAI scores and obtained an AJG rating 4 as a distinction journal. The Corporate Social Responsibility and Environmental Management journal has a 1 for AJG rating and occupied the 48th position in the AAIs measure. However, the Tourism Management journal, which also has a distinction rating on the ABS list, ranked as 47th in AAI. For our observations, not much agreement can be reached simply comparing between AJG and AAI ranking methods.

Conclusions
Many authors have studied and proposed methods and numerous indexes that provide alternative quality measures of different academic journals in diverse fields of study. In this research, the AAI method was applied in the sustainability field in social science journals as a preliminary study to offer some insights into the quality rating of journals. According to Chan et al. [19], the reasoning of AAI is that a prestigious journal tends to attract scholars from top-notch universities or institutions to publish their research work. Therefore, high AAI scores for a journal represents high journal quality because leading scholars produce quality research articles in general.
The results obtained demonstrate that there is a lower AAI score on average in the sustainability field compared with other disciplines such as finance, accounting, transportation, etc. The low scoring is probably caused by the high number of co-authors collaborating in environmental studies journals composed in the peer group. However, we have to bear in mind that, in addition to the sustainability studies category, many journals are also within the business or management disciplines which have shown a much lower number of authors on average in our sample. The average of AAI according to our sample can be interpreted as that, on average, 12.6% of journal articles in the chosen field are authored by academics or scholars from the top 50 ranking universities in our dataset. This result confirms an elite affiliation effect, in which leading sustainability journals have higher concentration of authors who are affiliated with elite institutions. However, such elite affiliation effects are very low, which can be caused by other factors (number of authors, etc.).
Comparing AAI ranking with other ranking measures, such as the JIF from Web of Sciences, SJR and SNIP from Scopus and AJG from Chartered Association of Business Schools, there are no consistent rating results obtained. The three citation-based ranking method (JIF, SJR and SNIP) has displayed relatively similar ranking results, especially for the top 10 rated journals. Only two journals, Annual Review of Environment and Resources and Review of Environmental Economics and Policy, align with the top 10 ranking journals in AAIs and the citation-based measures. To conclude, our AAI-based journal ranking is not correlated with the rankings in other measures.
Since AAI is based on the principle that as the percentage of authors in a journal who are from the top-ranking universities increases, the perceived value of that journal in terms of quality to these universities also increases. We confirm the publication by top-ranking universities with these postgraduate study subjects in the top-rated journals. Nevertheless, due to the large number of co-authors in the selected journals, we cannot observe a very high value of AAIs in this field.
However, we know that this method has certain limitations. Gorman and Kanet [23] have indicated that " . . . Any objective measure of journal quality, which is inherently subjective, will have its defects, but measures such as the AAI do provide value . . . " (p. 17). In this sense, we agree with Agrawal et al. [54] and Fry and Donohue [55] that the use of author affiliations to assess whether a journal is prestigious or not is still relatively new and it is necessary to continue analyzing it.
Another limitation is the complication encountered at the time of collecting information to separate academics by departments or areas of study in order to determine the journals they are attracted to present and publish their research work in. But we believe that our sample is representative in terms of selection of academics and journals related to sustainability issues.
Nevertheless, the use of author affiliations to assess the reputation of institutions and journals has been widely accepted and applied in many academic disciplines and by many authors. Therefore, we consider that the AAI is a method that provides an alternative ranking for journals besides other citation and survey-based ranking measures.
Similarly, we consider that productivity of scholars is not only measured by the journals in which the results of their research are published. Other aspects must be taken into account, but these aspects are beyond the purpose of this paper. Future research can be done to combine the AAI measure with other aspects for assessing quality of scholars' research work and journals. Other ranking criteria besides the QS Top University ranking can also be considered.