اقتصاد محیط زیست و محیطی در قرن 21st : زمان تنظیم تحلیل استنادی مقالات با نفوذ، مجلات، نویسندگان و نهادها

We investigate the influence of articles, authors, journals and institutions in the field of environmental and ecological economics. We depart from studies that investigated the literature until 2001 and include a time period that has witnessed an enormous increase of importance in the field. We adjust for the age effect given the huge impact of the year of an article's publication on its influence and we show that this adjustment does make a substantial difference — especially for disaggregated units of analysis with diverse age characteristics such as articles or authors. We analyse 6597 studies on environmental and ecological economics published between 2000 and 2009. We provide rankings of the influential articles, authors, journals and institutions and find that Ecological Economics, Energy Economics and the Journal of Environmental Economics and Management have the most influential articles, they publish very influential authors and their articles are cited most. The University of Maryland, Resources for the Future, the University of East Anglia and the World Bank appear to be the most influential institutions in the field of environmental and ecological economics.

We investigate the influence of articles, authors, journals and institutions in the field of environmental and ecological economics on the basis of citation analysis. Increasingly, performance measurement and impact analysis have come to play a role in research and education policy and in the assessment of departments and faculty. A lot of research is done on the assessment of the impact of journals and there is a lot of debate going on (see Harzing, 2010). It appears that in the classic journal impact factor, article age adjustment is missing. The conventional two and five year impact factors furthermore have the problem that they only use a two year and five year after publication window for papers to receive citations. We do not pursue this classic journal impact analysis but will rely on citation analysis. This type of analysis puts the article itself in the spotlight and not the journal. We think it is the article that makes the difference as the article is communicating the research. We are well aware of the fact that citations have their limitations too (see Costanza et al. (2004: 262)). For example, the influence of a paper need not be restricted to an academic audience, there is a bias to the journals that are in the database, and it takes time for citations to appear in the literature. However, authors such as Costanza et al. (2004) and Kim et al. (2006) are confident of the virtues of citation analysis to base their study on. We apply citation analysis to environmental and ecological economics, which has become an increasingly important field in both research and policy in the 21st century due to climate change, globalization, and the rapid advance of renewable energy. Citation analyses within environmental and ecological economics were first published in the 21st century, even though they mainly analysed 20th century publications due to the time required for citation and publication. Kohlstad (2000: 294) identifies “the most ‘useful’ (i.e. cited)” articles published in two sub-areas of environmental and ecological economics (energy economics and exhaustible resources economics) over five 5-year periods from 1974 to 1998. To define his sample, he searches for area specific keywords in 34 (general) economics journals. Kohlstad finds an age effect, as he observes older papers to receive more citations than younger peers with the exception of Perron's (1989) seminal econometric paper on oil price shocks. This result implies that citation counts might need to be annualized in some form when comparing journal articles. Kohlstad also lists the five journals with the highest number of citations per article in each sub-area during each decade in his sample and finds a noticeable degree of inconsistency among the top journals of each decade. This implies that journal rankings need to be updated regularly to reflect changes in journal impact. Furthermore, Smith (2000) reviews research on the non-market valuation of environmental resources published in the Journal of Environmental Economics and Management (JEEM) over the period 1978–1998. His review includes a list of all JEEM papers in this sub-area which have been cited more than 50 times by 1998. The list is dominated by older studies. This, again, implies that age can have an impact: the age effect, which we define as a significant positive relationship between the age of a study and its number of total citations. Ma and Stern (2006) analyse the overlap between JEEM and Ecological Economics (EcE) based on articles published between 1994 and 2003. They find high correlations between the journals citing JEEM and EcE as well as those journals referenced in JEEM and EcE, which implies a significant overlap between the two journals in specific areas and in the areas of environmental and ecological economics in general. Ma and Stern (2006) also list 30 articles which received the highest number of total citations in each journal. However, since they use total citations as their measure of influence, the youngest article in both lists is published in 1999, while the oldest appeared in 1931. Recently, two citation studies focus on evaluating journals in the field of environmental and ecological economics (Aufhammer, 2009 and Rousseau et al., 2009). However, both are fully exposed to the age effect discussed above and, in case of Aufhammer (2009), also to the biases associated with Google Scholar data (see, for instance, Jacsó, 2005, Jacsó, 2006a, Jacsó, 2006b, Jacsó, 2008 and Shultz, 2007). To the best of our knowledge, the only age adjustment in citation analysis of environmental and ecological economics to date has been conducted by Costanza et al. (2004). They examine the influence of 251 individual publications related to EcE which are published between 1920 and 2001. They assess articles nominated for their quality by the EcE Editorial board, highly cited articles published in EcE or articles and books published elsewhere that were highly cited by EcE articles. While Costanza et al. (2004: 264) mainly analyse total citations, they explicitly acknowledge that total citations as a measure of influence is biased towards older publications, which simply had more time to be cited. Hence, they do not only employ total citation as a measure of total influence but also calculate the “average number of citations per year … [as] ‘predictor’ of ultimate influence that can better compare older and younger articles”. This adjusted measure, for instance, aids the comparison of two of the most influential publications in their sample: Costanza et al.'s (1997) ‘Value of the world's ecosystems and natural capital’ and Hardin's (1968) ‘Tragedy of the Commons’. While the latter has more than five times more citations than the former (499 to 2525), since it is 29 years older, the former received marginally more citations per year (71.3 to 70.1) in Costanza et al.'s (2004) citation analysis. To sum up, the previous studies make substantial contributions to the understanding of influence and citation patterns in the increasingly important field of environmental and ecological economics. However, they do not assess the influence of individual authors or institutions and are, with the exception of Costanza et al. (2004), exposed to a substantial age effect. Costanza et al. (2004) implement their age adjustment only for individual articles published up to 2001, and no age adjusted ranking of articles published subsequently has been published to date. Similarly, no ranking of journals in the field of environmental and ecological economics has been published that adjusts for the age of a journal's most cited articles. If the article age effect is not controlled for in the journal rankings, the journals are virtually assessed on their performance in the earlier years of the data sample and improvements over time are inappropriately considered. Furthermore, journals vary the number of articles over time. Hence, journals which increased (decreased) their number of published articles during a sample period are disadvantaged (advantaged) due to the age effect which favours older over younger articles These gaps in the citation analysis literature of environmental and ecological economics provide us with the opportunity to employ an age effect adjusted citation analysis approach and a 21st century data sample. Therefore, we ask the following four research questions which are original in the context of our study: (1) Which are the influential articles published in environmental and ecological economics journals? (2) Which are the influential journals focused on publishing articles in environmental and ecological economics? (3) Which are the influential authors, who published in environmental and ecological economics journals? (4) Which are the influential institutions, whose affiliates published in environmental and ecological economics journals? In summary, this paper builds on previous citation analyses in the field of environmental and ecological economics or its sub-areas (Costanza et al., 2004, Kohlstad, 2000, Ma and Stern, 2006 and Smith, 2000). We extend their scope substantially by pursuing – to the best of our knowledge – a citation analysis of the field of environmental and ecological economics, which makes the following four contributions. First, we conduct the first analysis of the influential authors in the field. Second, we pursue the first investigation of the influential institutions in the area. Third, we conduct the first rating of journals in the field of environmental and ecological economics in the 21st century which is not exposed to age effect. Fourth, we compile the first list of the influential papers in the area published in this century, in which the importance of at least some areas of environmental and ecological economics dramatically increased (e.g. climate change, renewable energy). Our paper is structured in three further sections. In the following (second) section, we discuss our data set. Section 3 discusses our analysis and results with regard to each individual research question, before we conclude in the last section.

We investigate the influence of articles, authors, journals and institutions in the field of environmental and ecological economics. The main measure in our age adjusted analysis of the influence of articles, journals, authors and institutions is citations per year since publication (Cites p.a.) ( Costanza et al., 2004, Keloharju, 2008 and Schwert, 2007). Conceptually, Cites p.a. represent the ratio of the total citations received by an article divided by the decimal years passed since the article's publication. We depart from studies that investigated the literature until 2001 and include a time period that has witnessed an enormous increase of the academic and societal importance in the field. We adjust for age given the huge impact of the year of an article's publication on its influence. We analyse 6597 studies on environmental and ecological economics published between 2000 and 2009. On the basis of our analysis, we can come up with a clear perspective of what the most influential articles are, journals, and institutions. With respect to the influence of authors, we find it is much more complex and subjective. Hence, we are hesitant to conclude that one most influential author exists. Instead, we consider our results to indicate many influential authors, whose precise ranking depends considerably on the metric employed. As to the most influential articles, we find that De Groot et al. (2002) on classifying ecosystem attributes has 25 Cites p.a. and is to be regarded as the most influential paper in environmental and ecological economics published in the 21st century. Second is the review paper by Engel et al. (2008) with almost 17 citations per year. Lee's (2005) paper on energy consumption and GDP ranks third with 16 citations per year. The Turner et al. (2003) paper on valuing nature has almost 16 citations and is in the fourth place. We establish that Ecological Economics, Energy Economics and the Journal of Environmental Economics and Management have the most influential articles, publish very influential authors and are cited most. These three journals have to be regarded as the most influential. At the author level, we establish that the criterion used to assess author influence greatly matters. On the basis of (fractional) citations per year (see Gauffriau and Larsen, 2005), we find that Chien-Chang Lee, Sven Wunder and Stefano Pagiola rank first, second and third respectively. With the number of publications, Sven Wunder and Jayson Lusk rank first with six publications, before Chien-Chang Lee, Stephen Polasky, Ramazan Sari, and Ugur Soytas with five publications. On the basis of the fractional number of publications, we rank Lee first, Wunder second, and Lusk third. With regard to the overall fractional citations, David Stern is in the first place, before Chien-Chang Lee and Matthew Wilson. The University of Maryland, Resources for the Future, the University of East Anglia and the World Bank appear to be the most influential institutions in the field of environmental and ecological economics in the 21st century. These results build on previous citation analyses regarding environmental and ecological economics which predominantly focused on the 20th century (Costanza et al., 2004, Kohlstad, 2000, Ma and Stern, 2006 and Smith, 2000). We investigate the influential articles, authors and journals in the field on the basis of articles published in the 21st century when the field gained increasing academic and societal importance. Our analysis of the most influential institutions in the field has not been done before over any sample period. Our citation analysis is free from the age effect and our results highlight the relevance of an age adjustment especially for disaggregated units of analysis with structural age differences such as articles and authors. We furthermore find that more international editorial boards appear to be better in promoting their best journal articles than editorial boards originating from a small number of countries. As such, we think we have added value to the existing literature.