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Classifying economics for the common good: Connecting sustainable development goals to JEL codes

How does economics research help in solving societal challenges? This brief note sheds additional light on this question by providing ways to connect Journal of Economic Literature (JEL) codes and Sustainable Development Goals (SDGs) of the United Nations. These simple linkages illustrate that the themes of SDGs have corresponding JEL classification codes. As the mappings presented here are necessarily imperfect and incomplete, there is plenty of room for improvements. In an ideal world, there would be a JEL classification system for SDGs, a separate JEL code for each of the 17 SDGs.


Introduction
Economists play an increasingly important role in helping governments design new policies and regulations (Duflo 2017) but how does academic economics research help in solving global challenges? One way to analyse this is to explore the link between economic research and the Sustainable Development Goals (SDGs, LaFleur 2019). In 2015, the member states of the United Nations adopted 17 sustainable development goals, as part of the 2030 Agenda for Sustainable Development (United Nations 2015a). Great progress has been made but there is still a lot of work to do before achieving these goals (United Nations 2019). 2 Indexing and classification of documents are important since they decreases search costs and therefore promote efficient allocation of attention. In the context of economics research, Journal of Economic Literature (JEL) codes have been used to classify economic research since the early 20 th century (Cherrier, 2019). However, there does not yet exist an explicit JEL coding for sustainable development goals.
This brief note suggests that the existing classification systems of economic literature could be utilized to track how much attention is allocated within economics research to topics that are related to global challenges. The contribution of this brief note to existing literature is to connect SDGs to JEL codes. The remainder of the paper is organized as follows. Section 2 presents SDGs and JEL classification system. Section 3 links JEL codes and SDGs goal by goal and discusses the limitations. Section 4 concludes.

SDGs and JEL codes 2.1 SDGs
According to the United Nations, sustainable development is defined as "development that meets the needs of the present without compromising the ability of future generations to meet their own needs". 3  2 See e.g. SDG Tracker of Our World In data: https://sdg-tracker.org/ (Accessed on 21 March 2020), Sustainable Development Report: https://www.sdgindex.org/ (Accessed on 21 March 2020) and Sachs et al. (2019). 3 See https://www.un.org/sustainabledevelopment/development-agenda/ Accessed on 21 Mar 2020. 4 The MDGs were: Goal 1. Eradicate extreme poverty and hunger; Goal 2. Achieve universal primary education; Goal 3. Promote gender equality and empower women; Goal 4. Reduce child mortality; Goal 5. Improve maternal health; Goal 6. Combating HIV/AIDS, malaria, and other diseases; Goal 7. Ensure environmental sustainability; Goal 8. Develop a global partnership for development. See Millennium development goals: https://www.un.org/millenniumgoals/ SDGs: https://www.un.org/sustainabledevelopment/sustainable-developmentgoals/ Accessed on 21 March 2020. 5 See https://www.un.org/millenniumgoals/bkgd.shtml Accessed on 4 April 2020 Goal 1. End poverty in all its forms everywhere Goal 2. End hunger, achieve food security and improved nutrition and promote sustainable agriculture Goal 3. Ensure healthy lives and promote well-being for all at all ages Goal 4. Ensure inclusive and equitable quality education and promote lifelong learning opportunities for all Goal 5. Achieve gender equality and empower all women and girls Goal 6. Ensure availability and sustainable management of water and sanitation for all Goal 7. Ensure access to affordable, reliable, sustainable and modern energy for all Goal 8. Promote sustained, inclusive and sustainable economic growth, full and productive employment and decent work for all Goal 9. Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation Goal 10. Reduce inequality within and among countries Goal 11. Make cities and human settlements inclusive, safe, resilient and sustainable Goal 12. Ensure sustainable consumption and production patterns Goal 13. Take urgent action to combat climate change and its impacts Goal 14. Conserve and sustainably use the oceans, seas and marine resources for sustainable development Goal 15. Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss Goal 16. Promote peaceful and inclusive societies for sustainable development, provide access to justice for all and build effective, accountable and inclusive institutions at all levels Goal 17. Strengthen the means of implementation and revitalize the global partnership for sustainable development In order to get a rough overview of the occurrence of MDGs and SDGs in economics research during the past two decades, we conduct some very general keyword searches. Figure 2 shows the trends of simple keyword searches in IDEAS/RePEc bibliographic database 6 for both search queries "sustainable development goal" and "millennium development goal". As expected, the trends in the number of publications clearly show that SDGs have replaced MDGs after Agenda 2030 was introduced in 2015. It is also noteworthy that the increase in the number of research papers mentioning SDGs is growing very steeply.

JEL codes
In the field of economics, Journal of Economic Literature classification is the de facto standard in classifying articles (Cherrier 2017;Kosnik 2018). Majority of economics journals require authors to choose JEL codes which best describe their manuscripts when submitting (Kosnik 2018) and bibliographic databases such as IDEAS and SSRN allow users to browse articles by JEL codes. The first version of the JEL codes (or EconLit subject descriptors) by the American Economic Association (AEA) was published in 1911 and it has since been occasionally updated and extended (Cherrier 2017). According to the webpage of the AEA: "The JEL classification system was developed for use in the Journal of Economic Literature (JEL), and is a standard method of classifying scholarly literature in the field of economics. The system is used to classify articles, dissertations, books, book reviews, and working papers in EconLit, and in many other applications." 7 As of the beginning of 2020, there are 20 JEL categories, which have 122 second level subcategories that have altogether 856 third level sub-categories. Table 1 shows that the number of subcategories varies across main JEL classes. Interestingly, despite the important role of JEL codes, they have received only limited attention in research until recently (Cherrier 2017;Kosnik 2018).

Table 1. JEL codes
Notes: "General" JEL classes under 1st level codes with no 2nd level codes (e.g., B00 and C00) have been counted as 3rd level codes.

Methods and data
In an ideal or the first best world, there would be own JEL classification for SDGsthat is, a separate JEL code for each of the 17 SDGs. However, currently we live in a second best world without this type of classification. 8 In order to fill in this gap, we provide three simple ways to link JEL codes and SDGs. In principle, we could either link "each JEL code to the closest SDGs" or "each SDG to the closest JEL codes". We chose the latter option that is much simpler and link 17 SDGs to the most similar 3 rd level JEL codes. JEL code data was collected from the AEA's webpage and SDGs were collected from United Nations' webpage (see Section 2). Three alternative methods to establish links between SDGs and JEL codes are described next.
First, we extract keywords directly from the 17 SDGs (Section 2.1) and search over the keywords of 856 3 rd level JEL codes (Table 1) to document the number of potentially related JEL codes. For instance, the keyword for Goal 1 "End poverty in all its forms everywhere" is "poverty". Some SDGs are more broadly defined and are assigned more keywords correspondingly: For instance, the keywords for Goal 9 "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation" are "infrastructure", "industrialization" and "innovation".
We provide examples of JEL codes that most closely relate to the selected keywords.
Second, we build on LaFleur (2019) who created an SDG classification system for DESA publications. LaFleur (2019) was among the first to analyze United Nations publications using machine-learning approach to compute how much each SDG is represented in individual publications. 9 As part of his analysis, LaFleur (2019) used machine learning methods to identify keywords related to each SDG and we use a slightly modified version of his keyword list as a basis to match SDGs to JELs. For each SDG, we rank JEL codes according to the number of overlapping keywords. These keywords are presented in Table 2. We explore three different weightings for the keywords: 1) no weighting, 2) weight 1/1 for the 1 st keyword, 1/2 for the 2 nd , 1/3 for the 3 rd and so forth, and 3) weight 1 for the first five keywords and 1/[number of order] for the rest.
Third, we select three most relevant keywords for each SDG from the LaFleur's (2019) list based on elimination and discretion. First, we delete "general words" that clearly are not related solely to a specific SDG such as "change", "impacts", "patterns", "rapid", "added", "policies", "capita" and "nations". Second, we eliminate pairs of words when the same word-pair occurs also separately in the list. Third, in most cases we delete plural forms if the same word is on the list also as singular. Finally, from the remaining set of words, we select three words that most closely relate to corresponding SDG based on discretion. For most SDGs, we are left with three singular nouns as shown in Table 2. Table 3 reports the results of the simple keyword search approach. We also provide an example of a relevant JEL code for each keyword if there is one. This very simple keyword search already indicates that economic research classification can be relatively easily linked to SDGs. Only for some keywords no matching JEL codes are found (e.g., "girl", "sanitation").

SDG LaFleur (2019) keywords
Selected three  Table 3. Link between SDGs and JEL codes, simple keyword search Table 4 lists for each SDG three 3 rd level JEL codes that have the most overlap with keywords suggested by LaFleur (2019). We explored three different weightings based on the ranking of keywords and they produced relatively similar rankings for JEL codes. Table 4 reports the results for the third weighting option (see Section 3.1). For most SDGs, there are JEL codes that clearly have most keyword overlap with LaFleur's keywords, whereas for some the best matching JEL codes are not so unambiguous. In other words, there are several JEL codes with equal amount of keyword overlap. Most of the identified JEL codes seem to match SDGs quite well. One example of an exception is Goal 13 where JEL code C22 "Time-series models" overlaps in keywords but is not actually related specifically to the substance of Goal 13.  Table 5 is otherwise similar to Table 4 except that there the number of keywords for each SDG is limited to three most relevant ones (see Table 2). The resulting JEL codes are in most cases the same as in Table 4 but for some there is less overlap. For instance, for SDG 17 the top three JEL codes are all different in Tables 4 and 5. To summarize, these very simple keyword similarity analyses suggest that it is possible to connect SDGs and JEL codes. Thus, economists may classify their research articles to JEL codes that are closely linked to SDGs.  waste, air, pollution, management, safe R11 Regional Economic Activity: Growth, Development, Environmental Issues, and Changes issues related to regional economic activity including growth, development, and changes. Studies may also include the effects of agglomeration economies and foreign linkages (for example foreign direct investment or foreign trade) on regional economic activities. Includes environmental aspects of regional economics, such as the regional effects of climate change.   inequality, income O18 Urban, Rural, Regional, and Transportation Analysis • Housing • Infrastructure regional, urban, rural, and transportation issues related to economic development and developing economies, including urbanization.
cities, urban R11* Regional Economic Activity: Growth, Development, Environmental Issues, and Changes issues related to regional economic activity including growth, development, and changes. Studies may also include the effects of agglomeration economies and foreign linkages (for example foreign direct investment or foreign trade) on regional economic activities. Includes environmental aspects of regional economics, such as the regional effects of climate change.
cities, urban R12* Size and Spatial Distributions of Regional Economic Activity issues related to spatial distributions of economic activity including economic geography, interregional trade, and regional convergence. The mappings presented in Tables 3, 4 and 5 are examples of very simple ways to link JEL codes and SDGs and there are naturally multiple other ways. In other words, they are necessarily imperfect and incomplete and have several limitations. It is worth noting that some JEL codes cannot be directly linked to specific SDGs. For instance, economic methods (e.g., JEL code class C "Mathematical and Quantitative Methods" with its subclasses) are "general purpose technologies" and are not SDG-specific but can be applied to study all of them. It should also be noted that for some JEL codes the guideline mentions that documents classified to that specific JEL code may, or in some cases should, be "cross-listed" or "cross-classified" to other JEL codes. For instance, the guideline for JEL code "I15 Health and Economic Development" notes that it "covers studies about the impact of health on economic development, and the impact of levels of development on health. May cross-list with O15" (see Goal 3 in Table 4). Similarly, the guideline for JEL code "J83 Workers' Rights" notes that it "covers studies about labor standard issues related to workers' rights. Studies should be cross-classified here and under the other appropriate categories in J, if they are relevant." These nuances in JEL-code-specific guidelines were ignored in this article.

Discussion
As the sustainable development goals lack their corresponding JEL codes, this paper has suggested simple ways to connect SDGs and JEL codes. There are multiple ways to improve these linkages. For instance, one could use the corpus or keywords of economics articles that are tagged with a specific JEL code to establish the link to the closest SDGs. This would require much deeper bibliometric, topic modelling and science mapping analyses (cf. Aria & Cuccurullo 2017;Körfgen et al. 2018;Ambrosino et al. 2019;LaFleur 2019). These are left for future studies.