The Tipping Point in the Status of Socially Responsible Consumer Behavior Research? A Bibliometric Analysis

Looking at the impact of society on the environment or, as we write this manuscript in the midst of the COVID-19 crisis, the scenes of consumers hoarding products, we wonder if consumers really do exhibit socially responsible consumer behaviors (SRCB). An initial literature review showed that few studies have addressed this issue, which creates opportunities for the development of new research lines. Furthermore, no study had examined the conceptual evolution or whether SRCB is a developed or fragmented theme from an exhaustive compilation of all previous academic research. To address the proposed research questions, we conducted a bibliometric analysis applied to a corpus of manuscripts on SRCB indexed in the Web of Science (WoS) bibliographic database, from its inception in 1991 up to 2019. Co-word analysis provided a structure of conceptual sub-domains classified based on their density and centrality. In addition, thematic networks were extracted that showed the important associations between the main issues that the SRCB community has addressed, which enabled the authors to examine the subject’s intellectual structuring over almost three decades. The findings showed that the research, over time, has focused most on corporate social responsibility (CSR), this being a motor theme between 2013 and 2016. In general, SRCB has been a very fragmented field of study, however in the last three years, it has developed into a distinct entity; in the past, it was basically addressed through CSR. The most productive thematic areas during the last 30 years have been: (a) Research into consumer attitude, (b) research on CSR, and (c) research on social and sustainable consumption behavior. In response to calls for greater theoretical clarification of the SRCB discipline, the authors providing experts and novices with a better understanding of the current state of the art and suggest future research directions.


Introduction
Over the last years, studies in various scientific disciplines have examined research topics related to sustainability and socially responsible behavior. This statement is based on the fact that, little by little, awareness has grown that sustainable development must go hand in hand with social sustainability [1]. The depletion of resources, climate change, and global warming, beyond the challenge they pose in themselves, are results of the behaviors of those of us who inhabit the planet, in our different roles.
Business and management researchers have not been alien to this dynamic and have addressed the issue of sustainability from different perspectives: Corporate social responsibility [2][3][4], socially

RQ2:
To what extent is SRCB a developed or fragmented theme in the academic literature?
As this concept is important, it is worth asking from which perspectives it has been analyzed and to which other concepts it is related. SRCB research is quite fragmented, but there are obvious connections. This is the case for what has been called "ethical consumer behavior" that, according to Harrison et al. [59], describes consumers who "have political, religious, spiritual, environmental, social or other motives for choosing one product over another" and, as they added later, that "care whether a corporation promotes employees from minority ethnicities, plan their consumption to avoid harm to other animals, worry about product transportation distances and probably a plethora of other concerns". This is a broad concept that encompasses SRCB. Research into ethical consumer behavior "seeks answers about consumers' buying behaviors based on their attitudes [60,61], their ethical constraints [11,[62][63][64][65] and socio-cultural aspects" [38,66]. Another important concept with logical connections to socially responsible consumer behavior is "willingness to pay", or variants, such as the concept of "vote with the wallet". Becchetti and Salustri [67] defined "vote with the wallet as the propensity of consumers to consider social and environmental sellers' responsibility into consumption and saving choices", that is, consumers might use their spending power to influence companies' behaviors. In addition, other important concepts linked to SRCB are citizen consumption, healthy consumption, and social commitment. These points give rise to a further research question: RQ3: What other themes are linked to SRCB research?
According to the Web of Science (WoS) bibliographic database, the first article in this research field was published in 1991. In it, Singhapkdi and Latour [68] examined the public policy issues of an anti-littering campaign. In pursuit of various objectives, they determined, in particular, the relationship between socially responsible consumption (SRC) orientation and voting intentions with respect to a litter-related issue. Since then, several hundred related works have been published in prestigious journals; it will be of interest now for academia to consider the state of the art and the current status of the different themes that have evolved. It is worth asking whether these issues have evolved in parallel, or whether they are connected to developments in political and social positioning. Therefore: RQ4: How have these themes evolved since 1991? RQ5: What are the most important themes and subject areas in terms of academic output?
The fragmentation of SRCB research, the dynamic nature of this and related concepts, together with the global crisis that is being suffered in 2020, make it necessary to redefine the concept. To address these research questions, we conducted a descriptive bibliometric study of SRCB articles published in the Web of Science (WoS)-listed international journals, as described in the methodology section.

Bibliometrics and Co-Word Analysis Procedure
The first definition of bibliometrics was "the application of mathematics and statistical methods to books and other media of communication" [69]. Bibliometric analysis has been used in disciplines as diverse as management information systems [70], financial marketing [71], integrated marketing communications [72], hospitality [73], and key account management [74], among others.
Bibliometrics employs a wide range of techniques, author and document co-citation analysis, co-word and textual analysis [60], using multivariate methods. In document co-citation analyses, the documents with the most impact within a research field are identified, and assessments are made of the matrix of co-citation frequencies between document pairs [75]. Callon, Courtial, and Penan [76] identified two main groups of bibliometric measures, productivity measures and relatedness measures. Productivity measures analyze scientific activity based on statistics and document characteristics, such as author(s), citation(s), and sources, regardless of whether there is a relationship between them. However, relatedness measures do take into account similarities between documents.
Keywords are the terms that characterize a study's main ideas, and provide indications of the research trend that its authors are following [77]. 'Co-word analysis' is relational [76], as it measures the co-occurrence or joint occurrence of keywords extracted from each document, from which matrices of co-occurrences are constructed and similarity measures calculated.
Co-word analysis is one of the most suitable methods for discovering trends and emerging issues in scientific fields; the present study is the first to use co-word analysis in a literature review of SRCB. Specifically, co-word analysis is based on the analytical method proposed by Cobo et al. [78] (Yang et al. [79] took a similar approach), and goes through the following stages: (a) Bibliometric data recovery, (b) data processing and extraction, (c) normalization and calculation of bibliometric indicators, (d) mapping, (e) analysis, and finally, (f) visualization of science maps and thematic networks.
The co-word analysis in the present study was conducted using SciMAT ( [24]; Sci 2 s, 2011). SciMAT is an open source (GPLv3) software program designed by the Sci 2 s research group at the University of Granada [24]. Science maps, based on an analysis of the co-occurrence of the keywords that characterize each article, can be created using SciMAT. These maps enable us to monitor scientific fields by defining the relevant research areas, which allows us to understand their intellectual, social, conceptual, and cognitive frameworks, and to analyze their structural evolution [24]. Each cluster (research topic or thematic subnetwork) can be characterized using two parameters [80]: • Centrality: This measures the degree of interaction among clusters (or themes, topics); that is, the strength of the external links that exist among clusters. This value can be understood as a measure of the importance of a theme in the development of the entire field of research under analysis.

•
Density: This measures the internal strength of a cluster; that is, the strength of the internal links between the keywords that describe this research topic. This value can be considered as a measure of the degree to which the topic under study has been developed.
Applying these parameters, two types of network are identified. Principal themes have high centrality and density values, while isolated themes have low centrality values (see Callon et al. [80]). Figure 1 provides an example of a strategic diagram. In this way, a research field can be divided into a set of themes, represented two-dimensionally, and classified into four groups [75,76,78,80], as follows:

1.
Themes in the upper right-hand quadrant (I) can be considered well-developed and important for the structuring of the research field in question. These are known as the "motor themes" of the specialist topic, as they have strong centrality and high density. In everyday parlance, we might call these mainstream themes.

2.
Themes in the upper left-hand quadrant (II) present highly developed internal links, but their external links are irrelevant, hence they are considered of only marginal importance for the research area. These themes are extremely specialized and peripheral in nature.

3.
Themes in the lower left-hand quadrant (III) are marginal and underdeveloped. They present low levels of density and centrality, and mainly pertain to emerging or declining themes.

4.
Themes in the lower right-hand quadrant (IV) are stable. That is, they are important to the research field in question, but they are not developed. They can be classified as transversal, basic (general) themes.
Sustainability 2020, 12, x FOR PEER REVIEW 5 of 24 • Density: This measures the internal strength of a cluster; that is, the strength of the internal links between the keywords that describe this research topic. This value can be considered as a measure of the degree to which the topic under study has been developed.
Applying these parameters, two types of network are identified. Principal themes have high centrality and density values, while isolated themes have low centrality values (see Callon et al. [80]). Figure 1 provides an example of a strategic diagram. In this way, a research field can be divided into a set of themes, represented two-dimensionally, and classified into four groups [75,76,78,80], as follows: 1. Themes in the upper right-hand quadrant (I) can be considered well-developed and important for the structuring of the research field in question. These are known as the "motor themes" of the specialist topic, as they have strong centrality and high density. In everyday parlance, we might call these mainstream themes. 2. Themes in the upper left-hand quadrant (II) present highly developed internal links, but their external links are irrelevant, hence they are considered of only marginal importance for the research area. These themes are extremely specialized and peripheral in nature. 3. Themes in the lower left-hand quadrant (III) are marginal and underdeveloped. They present low levels of density and centrality, and mainly pertain to emerging or declining themes. 4. Themes in the lower right-hand quadrant (IV) are stable. That is, they are important to the research field in question, but they are not developed. They can be classified as transversal, basic (general) themes. These themes and their interconnections with other keywords can be drawn in one network graph. A particular "thematic network" can be labelled with the name of the most significant keyword in the associated theme (usually the most central node or keyword of its associated thematic network). The volume of the spheres is proportional to the number of documents related to each keyword and number of citations, and the density of the link between the two spheres i and j is proportional to the co-occurrence of both. In addition, in evolution maps, a measure of overlap between themes can be used, such as, for example, in the Jaccard index (cij/(ei + e − cij))) [24].

Data Collection
Journal articles were chosen as assessment units, as the academic community acknowledges them as the most advanced and up-to-date knowledge sources, widely used in literature reviews in the marketing (and, more generally, management) field (e.g., [81]). In addition, the descriptions of These themes and their interconnections with other keywords can be drawn in one network graph. A particular "thematic network" can be labelled with the name of the most significant keyword in the associated theme (usually the most central node or keyword of its associated thematic network). The volume of the spheres is proportional to the number of documents related to each keyword and number of citations, and the density of the link between the two spheres i and j is proportional to the co-occurrence of both. In addition, in evolution maps, a measure of overlap between themes can be used, such as, for example, in the Jaccard index (c ij /(e i + e − c ij) )) [24].

Data Collection
Journal articles were chosen as assessment units, as the academic community acknowledges them as the most advanced and up-to-date knowledge sources, widely used in literature reviews in the marketing (and, more generally, management) field (e.g., [81]). In addition, the descriptions of SRCB and the evolution of SCRB research enabled us to specify keywords that could function as queries in bibliometric databases.
Based on this query, a total of 441 references to documents were downloaded from the WoS Core Collection, including author keywords, Keywords Plus, abstracts, and citation measures. Of this total, 92 were available in open access format, and the remainder (350) in restricted access. In bibliometric studies such as this, a large percentage of documents relate to other disciplines, either because of the polysemic nature of the terms used or, occasionally, because they are given as examples in the abstracts. Thus, in our review of the content, some documents were removed; among others, these related to geography (10), nutrition and dietetics (4), biotechnology and applied microbiology (3), computer science and cybernetics (2), information science and library science (2), and language and linguistics (2). At this stage of the data processing some duplicate records were also detected and removed.
The timeframe for our study was from 1991 (first paper), and we returned a total of 340 valid articles, 69 of which were open access. Figure   SRCB and the evolution of SCRB research enabled us to specify keywords that could function as queries in bibliometric databases. Hence, by using terms such as 'socially responsible consumer(s) behavior', 'socially responsible consumer(s)', 'consumer(s) social responsibility', 'socially responsible purchasing behavior', 'ethical consumer(s)', 'consumer(s) ethical behavior', 'consumer(s) ethical consumption', 'consumer(s) ethical value(s)', 'responsible consumer attitude(s)', 'responsible consumer(s) decision-making', 'consumer(s) moral responsibility', 'consumer(s) sustainable behavior', and 'consumer(s) sustainable consumption', we ensured that we covered the entire spectrum of SRBC articles. In particular, the following query was used in the WoS bibliographic base: #Query: TS= ("Socially responsible consumer behavio*" OR "Socially responsible consumers behavio*" OR "Socially responsible consumption behavio*" OR "Socially responsible consumer*" OR "Sociallyresponsible consumption" OR "Consumer* social responsibility" OR "Socially responsible purchasing behaviour*" OR "Ethical consumer*" OR "Consumer* ethical behavio*" OR "Consumers ethical consumption" OR "Consumer* ethical value*" OR "Responsible consumer attitude*" OR "Responsible consumer decision-making" OR "Consumer* moral responsibility" OR "Consumer* sustainable behaviour*" OR "Consumer* sustainable consumption") where the field TS refers to a search based on the "topic" ('topic' = 'title' + 'keyword' + 'abstract'), refined by document type (paper, proceedings, review, or other).
Based on this query, a total of 441 references to documents were downloaded from the WoS Core Collection, including author keywords, Keywords Plus, abstracts, and citation measures. Of this total, 92 were available in open access format, and the remainder (350) in restricted access. In bibliometric studies such as this, a large percentage of documents relate to other disciplines, either because of the polysemic nature of the terms used or, occasionally, because they are given as examples in the abstracts. Thus, in our review of the content, some documents were removed; among others, these related to geography (10), nutrition and dietetics (4), biotechnology and applied microbiology (3), computer science and cybernetics (2), information science and library science (2), and language and linguistics (2). At this stage of the data processing some duplicate records were also detected and removed.
The timeframe for our study was from 1991 (first paper), and we returned a total of 340 valid articles, 69 of which were open access. Figure   Prior to conducting the co-word analysis, we performed a normalization process to merge plural and singular forms (e.g., 'consumer'/consumers, 'brand'/'brands') and to convert acronyms into their Prior to conducting the co-word analysis, we performed a normalization process to merge plural and singular forms (e.g., 'consumer'/consumers, 'brand'/'brands') and to convert acronyms into their full forms. We also undertook a semantic search to group together words written in different ways (keeping the meanings unchanged). Principally, these affected words spelled differently in American and British English, such as 'behavior' and 'behaviour', and those that can be hyphenated or unhyphenated (e.g., 'socially-responsible'/'socially responsible'). The total number of keywords processed was 1464, an average of 4 keywords per manuscript.
Our analysis of specific periods identified future trends (emerging/declining themes) and relationships that might have seemed insignificant within the context of an overall timeframe covering topics extensively studied in the past, but less so today [82]. As to the length of the periods, as is normal in longitudinal co-word analyses, we made the first period the longest, to achieve a sufficient number of published manuscripts; we divided the second and third periods into blocks of 3 years or so to give us a significant volume of documents and also to take into account major milestones in the development of the discipline. Thus, the present study examines three sets of data, for the periods 1991-2012, 2013-2016, and 2017-2019, the first covering 22 years, the second and third, 3 years.
Our criteria for generating the networks and reducing the data were that the keywords had to have appeared more than 2 times in the different periods, with minimum co-occurrence values of 2. Ss bibliometric quality indicators, we used the h-index of the keyword and the average and the sum of citations received up to the date when the data were downloaded. The number of articles for each period is shown in Figure 3.
full forms. We also undertook a semantic search to group together words written in different ways (keeping the meanings unchanged). Principally, these affected words spelled differently in American and British English, such as 'behavior' and 'behaviour', and those that can be hyphenated or unhyphenated (e.g., 'socially-responsible'/'socially responsible'). The total number of keywords processed was 1464, an average of 4 keywords per manuscript.
Our analysis of specific periods identified future trends (emerging/declining themes) and relationships that might have seemed insignificant within the context of an overall timeframe covering topics extensively studied in the past, but less so today [82]. As to the length of the periods, as is normal in longitudinal co-word analyses, we made the first period the longest, to achieve a sufficient number of published manuscripts; we divided the second and third periods into blocks of 3 years or so to give us a significant volume of documents and also to take into account major milestones in the development of the discipline. Thus, the present study examines three sets of data, for the periods 1991-2012, 2013-2016, and 2017-2019, the first covering 22 years, the second and third, 3 years.
Our criteria for generating the networks and reducing the data were that the keywords had to have appeared more than 2 times in the different periods, with minimum co-occurrence values of 2. Ss bibliometric quality indicators, we used the h-index of the keyword and the average and the sum of citations received up to the date when the data were downloaded. The number of articles for each period is shown in Figure 3.

SRCB Literature Publication Activity: The Most Prolific Authors and Journals
Next, we carried out a basic analysis of the authors who were most active in the SRCB scientific community. The most prolific author in the 30-year period was D. Shaw, who published nine articles between 2002 and 2016, as shown in Table A1 in Appendix A. Shaw appears with Newholm in four of the nine published works. The second most prolific author, with seven articles, was E. Papaikonomou. Just over half of these (57.14%) were co-written with G. Ryan. Next, with five papers, was D.

SRCB Literature Publication Activity: The Most Prolific Authors and Journals
Next, we carried out a basic analysis of the authors who were most active in the SRCB scientific community. The most prolific author in the 30-year period was D. Shaw, who published nine articles between 2002 and 2016, as shown in Table A1 in Appendix A. Shaw appears with Newholm in four of the nine published works. The second most prolific author, with seven articles, was E. Papaikonomou. Just over half of these (57.14%) were co-written with G. Ryan. Next, with five papers, was D. According to WoS, the 10 most cited articles are those listed in Appendix A (Table A2). With more than 300 citations, Maignan [27] and Carrington et al. [84] stand out. Maignan [27], taking a cross-cultural approach, examined the predisposition of consumers to support socially responsible organizations and their perceptions of the economic, legal, ethical, and philanthropic responsibilities of companies. Carrington et al. [2010] proposed a holistic conceptual model that addressed the gap between the purchase intentions and the actual buying behavior of ethically minded consumers.
The journals that published the most articles in the field were the Journal of Business Ethics (40 documents; see Table A3), the International Journal of Consumer Studies (15), Sustainability (8), Social Responsibility Journal (7), European Journal of Marketing (6), Journal of Agricultural and Environmental Ethics (6), and the Journal of Marketing Management (6).

Conceptual Evolution of SRCB
Strategic diagrams (Figure 4, Figures 5 and 7) were created to analyze the most important topics in the area for each period. The size of the spheres is proportional to the number of documents linked to the concepts in question.
According to WoS, the 10 most cited articles are those listed in Appendix A (Table A2). With more than 300 citations, Maignan [27] and Carrington et al. [84] stand out. Maignan [27], taking a cross-cultural approach, examined the predisposition of consumers to support socially responsible organizations and their perceptions of the economic, legal, ethical, and philanthropic responsibilities of companies. Carrington et al. [2010] proposed a holistic conceptual model that addressed the gap between the purchase intentions and the actual buying behavior of ethically minded consumers.
The journals that published the most articles in the field were the Journal of Business Ethics (40 documents; see Table A3), the International Journal of Consumer Studies (15), Sustainability (8), Social Responsibility Journal (7), European Journal of Marketing (6), Journal of Agricultural and Environmental Ethics (6), and the Journal of Marketing Management (6).

Conceptual Evolution of SRCB
Strategic diagrams (Figures 4, 5 and 7) were created to analyze the most important topics in the area for each period. The size of the spheres is proportional to the number of documents linked to the concepts in question.

1991-2012
During the first period (1991-2012), the field of study revolved around 12 main themes, or concepts (see Figure 4). Almost all are classified as basic (quadrant IV), or very specialized (quadrant II). The concepts most often highlighted by the authors, whether in the title, abstract, or keywords, were "ethics" and "fair trade". These two themes were associated with the greatest number of documents (19 and 15, respectively), citations (1076 and 1234, respectively), and h-index values (16 and 13, respectively).

1991-2012
During the first period (1991-2012), the field of study revolved around 12 main themes, or concepts (see Figure 4). Almost all are classified as basic (quadrant IV), or very specialized (quadrant II). The concepts most often highlighted by the authors, whether in the title, abstract, or keywords, were "ethics" and "fair trade". These two themes were associated with the greatest number of documents (19 and 15, respectively), citations (1076 and 1234, respectively), and h-index values (16 and 13, respectively).
This can be seen in Table 2, which shows the performance measures of the different topics for each period. Both concepts (ethics and fair trade) have high centrality (52.11 and 57.04, respectively), which means they have strong external links with other networks. These are, therefore, very important themes in the development of the research field.  In fact, "fair trade" is clearly positioned as a 'motor' concept in this period (quadrant I), that is, it is an important theme for the structuring of the research field. Its corresponding thematic network shows that at this stage, it was cited in works that addressed general aspects such as consumption and ethical consumption and, to a lesser extent, with aspects such as branding and the theory of planned behavior.
All the studies carried out in this period co-occurred with "fair trade", which thus emerged as a theme, exceeding the established thresholds. The basic concept "ethics" positioned itself in this period as a candidate to become a motor theme in socially responsible consumer research; however, it failed to appear as a theme in the following periods. In this period, "ethics" was strongly related to keywords such as consumer and consumer behavior and, to a lesser extent, with cultural dimensions and marketing and management (which itself became a peripheral theme in the second period).
Other important concepts in this period, positioned as basic themes, were "country-areas", "attitude", and "behavior". The works applied to different countries or areas also addressed aspects such as CSR, consumer decision-making, and beliefs and motivations. It is curious that CSR appeared only as a term linked to "country-areas" in its corresponding network, and not as a principal concept; its co-occurrence, centrality, and density are insufficient to position it in the strategic diagram. "Attitude", meanwhile, was related to ethical consumer, religion, and organization, and "behavior" was related to personal values, social responsibility, and perception.
Other peripheral themes (quadrant II) with well-developed internal and external links were "economy", "sustainable consumption behavior", "production", and "social media", which are considered of marginal importance in this field of research.
The generic theme "socially responsible consumption behavior" (seven papers) appeared in this period. This encompassed any type of socially responsible consumption, for example, the purchasing environment of the consumer experience ("SRCB"). It should be noted that SRCB, as such, did not form part of the research carried out during this initial stage. However, the thematic network, which included related studies, reflected the presence of SRCB as a subordinate concept of "environmental orientation", which is positioned in the diagram as an 'emerging' theme (quadrant III), and which fragmented into different environmental issues in the following periods. Thus, in this period, SRCB was not examined as a freestanding entity, but authors began to include it as part of other approaches or orientations.

2013-2016
In the second period (2013-2016), the co-word analysis showed that the field of study revolved around 16 concepts ( Table 2). The diagram at Figure 5 shows the high fragmentation of the terms, clearly highlighting "attitude" and "CSR" as motor issues with strong weights in the development of the area. These two concepts were not only associated with the greatest number of documents published during this period (28 each), they also have the highest performance indicators: Number of citations (579 and 456, respectively) and h-index (13 and 12, respectively).  This can be seen in Table 1, which shows the performance measures of the different topics for each period. Both concepts (ethics and fair trade) have high centrality (52.11 and 57.04, respectively), which means they have strong external links with other networks. These are, therefore, very important themes in the development of the research field.   "Attitude" also presented the highest centrality value (94.2), and was strongly related to ethical consumer, consumer behavior, ideology, and fair trade. CSR had a centrality value of 66.35, and was related to business, behavior, responsibility, and "SRCB". Among the motor themes, "consumption" and "sociocultural factors" should be highlighted, each with 11 documents and an important number of citations (369 and 131, respectively) and h-index values (8 and 5). "Consumption", which had the lower centrality and density of the two, was strongly associated with the satellite terms cross-cultural and habit. Other words linked to "consumption" were organic product and consumerism. "Sociocultural factors" showed a strong relationship with value, and was linked to ecology, consumer culture, and environmental orientation. This last term did not achieve enough weight to become thematic.
"Branding" and "identity" appeared as basic themes, and the "theory of planned behavior" and "marketing and management" appeared as peripheral or specialist topics. "Branding" appeared in its related thematic network associated with ethics, perception, anti-consumption, and conceptual framework. "Identity", meanwhile, appeared associated with product, ethical consumption, food and beverage, and cultural dimensions.
On the other hand, the specialist theme of the "theory of planned behavior" included only two terms in its thematic network, personal values and intention. Finally, "marketing and management" was linked only to satisfaction.
As in the previous period, "SRCB" still did not have its own freestanding identity, thus it does not appear in the diagram, despite being associated with 14 documents. However, it was developing as a satellite theme of "corporate social responsibility" ("CSR") and, as we can see in Figure 6, it was linked to issues such as business and behavior in a general approach.

2017-2019
In the final period (2017-2019), we can see that the number of terms related to the field of knowledge increased to 18 (Table 1). It can also be seen that a greater number of motor issues emerged, included in a significant number of documents. The term with the highest centrality (86.29) and density (26.93) in this quadrant was "organic product", which was linked to words/terms such as shopping, product, attitude, and, again, the theory of planned behavior, but did not achieve autonomy as a stand-alone subject. "Ethical consumer", a motor theme, stands out as it was associated with the most documents. The main words/terms associated with it were "moral", behavior, and beliefs and motivations.
"Sociocultural factors" was again a motor theme in this period, but the term took on a new focus. In the second period, it was linked to value, ecology, consumer culture, and environmental orientation, but in the third, it was related to satellite themes such as sustainable consumption behavior, green consumer, anti-consumption, and, again, environmental orientation. The last motor theme was "knowledge and information", which was associated with works on service, quality, consumption, and CSR. In fact, "CSR" ceases to be a "pure" theme, and in this period, it evolved towards a more applied theme that addressed the previously listed aspects.
"Multivariate data analysis" techniques appeared in this period, mainly through the application of tools such as cluster-analysis (specifically, K-means procedures), factor analyses, and structural equation modelling (including PLS-SEM-based techniques). These techniques were applied in articles on consumer decision-making, ideologies, marketing consumer research, and, finally, measurement and scales.
The basic topics, among which were "consumer" and "SRCB", are grouped in the lower-right quadrant of Figure 7. The topic "consumer" (13 papers) adopts a general meaning here; that is, topics not specifically contained within other approaches, such as ethical consumer or "SRCB", to mention two concrete examples. In particular, in this period, we found it in papers dealing with social media, communication, other theories, and socially responsible consumption behavior. "SRCB" was associated with 12 documents in this period, somewhat similar to its performance in the previous period. However,

2017-2019
In the final period (2017-2019), we can see that the number of terms related to the field of knowledge increased to 18 (Table 2). It can also be seen that a greater number of motor issues emerged, included in a significant number of documents. The term with the highest centrality (86.29) and density (26.93) in this quadrant was "organic product", which was linked to words/terms such as shopping, product, attitude, and, again, the theory of planned behavior, but did not achieve autonomy as a stand-alone subject. "Ethical consumer", a motor theme, stands out as it was associated with the most documents. The main words/terms associated with it were "moral", behavior, and beliefs and motivations.
"Sociocultural factors" was again a motor theme in this period, but the term took on a new focus. In the second period, it was linked to value, ecology, consumer culture, and environmental orientation, but in the third, it was related to satellite themes such as sustainable consumption behavior, green consumer, anti-consumption, and, again, environmental orientation. The last motor theme was "knowledge and information", which was associated with works on service, quality, consumption, and CSR. In fact, "CSR" ceases to be a "pure" theme, and in this period, it evolved towards a more applied theme that addressed the previously listed aspects.
"Multivariate data analysis" techniques appeared in this period, mainly through the application of tools such as cluster-analysis (specifically, K-means procedures), factor analyses, and structural equation modelling (including PLS-SEM-based techniques). These techniques were applied in articles on consumer decision-making, ideologies, marketing consumer research, and, finally, measurement and scales.
The basic topics, among which were "consumer" and "SRCB", are grouped in the lower-right quadrant of Figure 7. The topic "consumer" (13 papers) adopts a general meaning here; that is, topics not specifically contained within other approaches, such as ethical consumer or "SRCB", to mention two concrete examples. In particular, in this period, we found it in papers dealing with social media, communication, other theories, and socially responsible consumption behavior. "SRCB" was associated with 12 documents in this period, somewhat similar to its performance in the previous period. However, we now see it mainly related to personality traits, impact, citizen consumption, and perspective, in general (see Figure 8).  "Public good" and "cause-related marketing" stand out as specialist themes (quadrant II). Finally, standing out in the zone with emerging and declining themes (quadrant III) are works on "sustainability", in general, and "green sustainable product". "Sustainability" was linked to concepts such as globalization, macromarketing, strategy, and cross-cultural approaches. "Green sustainable product" is a more specific theme, directly linked in this discipline to the socially responsible  "Public good" and "cause-related marketing" stand out as specialist themes (quadrant II). Finally, standing out in the zone with emerging and declining themes (quadrant III) are works on "sustainability", in general, and "green sustainable product". "Sustainability" was linked to concepts such as globalization, macromarketing, strategy, and cross-cultural approaches. "Green sustainable product" is a more specific theme, directly linked in this discipline to the socially responsible "Public good" and "cause-related marketing" stand out as specialist themes (quadrant II). Finally, standing out in the zone with emerging and declining themes (quadrant III) are works on Sustainability 2020, 12, 3141 13 of 23 "sustainability", in general, and "green sustainable product". "Sustainability" was linked to concepts such as globalization, macromarketing, strategy, and cross-cultural approaches. "Green sustainable product" is a more specific theme, directly linked in this discipline to the socially responsible consumer. This theme was related to works that studied fashion in clothing and shoes, consumer generations, and motivations from a marketing management perspective. The theme "willingness to pay" appears very close to the origin of the coordinates, and it could be an emerging or disappearing theme in the coming years; its thematic network was associated with cultural dimensions, religion, agriculture, and food and beverage. Research "methodology" (related to different approaches, phases, and types of research) appeared quite frequently in this period, linked to other themes such as retailing, social responsibility and tourism, and to countries and geographical areas.

Structural Analysis of the Evolution of Research Dealing with SRCB
In addition to identifying topics and analyzing them by periods, using SciMAT, it is possible to observe their evolution over time. The thematic areas in which SRCB research is developing are shown in Figure 9 (and Table 2). The solid lines in the figure indicate a thematic nexus based on the fact that both topics (or clusters) share the same name, or the name of one topic is (partly) linked to another. The dotted lines indicate that topics are related because they share keywords. The thickness of the lines is proportional to the inclusion index, and the size of the spheres is proportionate to the number of works published on the topic [85].
As can be seen in Figure 9, studies carried out over the three periods did not show any great cohesion. It can be observed that most of the issues detected are not grouped together under themes that appeared in previous or following periods. In fact, only three themes were repeated in two study periods, "attitude", "sociocultural factors", and "country and area".
In addition, it was observed that scientific output was concentrated around eight thematic approaches or areas. Within these, there were two quite clear approaches, research into "attitude" and "CSR". The other SRCB research approaches over time showed less consistency or cohesion. The following describes the approaches:

A.
Research on consumers' attitudes towards ethical consumption. The theme "attitude" showed significant cohesion throughout the period, including in its structural evolution topics such as "fair trade", "organic products", and "ethical consumer". It should be emphasized that all the concepts of this approach are motor issues in their corresponding time periods. B.
Research on CSR. A second approach that clearly emerged is what we can call "CSR", which includes "behavior", "knowledge and information", "business", and "SRCB". In this case, "CSR" and "knowledge and information" are motor issues in their respective periods. The volume of documents on the two themes ( Table 2) that shape the two identified approaches shows that both approaches will contribute significantly to the development of SRCB research. C.
Research on sociocultural factors under the auspices of environmental orientation. This may be the most concrete thematic area among these less established approaches, which include topics such as "environmental orientation" and "sociocultural factors". In particular, "sociocultural factors" was a motor theme in the second and third periods analyzed. D.
Research on social and sustainable consumption behavior. These terms apply to the approach taken by various evolving studies, whose central theme is "socially responsible consumption behavior" or "sustainable consumption behavior". These highlight different "countries and areas" of application and focus on "consumer decision-making", with reference, in the last period, to the "methodology" used. E.
Research on identity and willingness to pay. This approach, which again covers all three periods, is based on the relationships established between "measurement and scales", "identity", and "willingness to pay". F. Research on 'Ethos Marketing'. This approach emerged in the first study period with "ethics" and is linked to "marketing and management" and "branding" in the second period. "Ethos" is most important for brand management and brand reputation, since it defines the what and why of the brand. Perhaps its development could be extended into the third period through the link established between "marketing and management" and "green sustainable product", that is, cohesion with the following ("green" concern) approach. G.
Research on 'green' concern. "Green" concern is an approach that emerged in the second period, related to the cluster "clothing, shoes, and fashion" and, thereafter, with the third period clusters "green sustainable product" and "green", from 2012 to the present. H.
Established theory-based approaches. Finally, this approach was developed from articles that, in the last two periods, presented a solid theoretical framework ("other theories") about the "consumer". As can be seen in Figure 9, studies carried out over the three periods did not show any great cohesion. It can be observed that most of the issues detected are not grouped together under themes that appeared in previous or following periods. In fact, only three themes were repeated in two study periods, "attitude", "sociocultural factors", and "country and area".
In addition, it was observed that scientific output was concentrated around eight thematic approaches or areas. Within these, there were two quite clear approaches, research into "attitude" and "CSR". The other SRCB research approaches over time showed less consistency or cohesion. The following describes the approaches: As a final corollary, from the perspective of the consumer, our research showed that corporate social responsibility (CSR) only appears as a freestanding entity in the second period, in which it was also a motor theme. However, a more detailed analysis shows that in the other two periods, it formed part of other thematic networks, appearing in a relatively large number of documents (69). Thus, we can confirm Vitell's (2015) statement, in the introduction to the work, that "the literature is replete with articles emphasizing the importance of corporate social responsibility" (p. 767).
Sustainability only appears as a distinct entity in the third period, but in the first two periods, it appeared in 32 articles. SRCB appeared as a distinct entity only in the third period, specifically in 38 documents. Therefore, we can conclude that the research, over time, has focused most on CSR, but sustainability and SRCB now attract a similar level of attention in the academic literature analyzed in the third period, although, if all three periods are taken into account, they remain far behind CSR in quantitative terms.

Discussion of Results
The analysis of the study period, which examined in particular motor themes and the words most linked to the SRCB research carried out, yielded as a first result a conceptualization proposal. Thus, the SRCB consumer can be defined as one who exhibits a favorable attitude towards organic and fair-trade products and, in general, towards products associated with socially responsible practices. (S)he understands that consumption is a means of exercising socially responsible citizenship.
An important conclusion that can be drawn from the last period of research analyzed (2017-2019) is that researchers focused on a new consumer type, the 'ethical consumer'. While this ethical consumer is complex and multi-dimensional, (s)he seems to share certain characteristics with the SRCB consumer. In this sense, those studies that will, in the future, closely examine important aspects, such as the way in which personal and sociocultural factors configure different profiles, or levels, of SRCB, might establish whether for some profiles, or some levels (assuming they exist), that the SRCB and ethical consumer concepts overlap.
Having interpreted the co-word analysis, we are able to answer the research questions posed at the beginning of the present study.
"Has academic research been more focused on CSR and sustainability than on the role of consumers and their socially responsible behavior?" (RQ1) The academic research has, over time, been more focused on CSR, with the topic being a motor theme in the second period. Sustainability, as an emerging topic, and SRCB, as a basic topic, attracted a similar level of attention in the literature analyzed in the third period, although if all three periods are taken into account, they remain far behind CSR in volume terms.
"To what extent is SRCB a developed or fragmented theme in the academic literature?" (RQ2) In particular, and responding to the title of the present study, it can be concluded that the beginning of the second decade of the 21st century was the turning point ( Figure 2). It can be seen that from the beginning of that decade, greater interest began to be shown in SRCB, and this trend accelerated from its mid-point. It is clearly an emerging theme.
It can be said that SRCB research has hitherto been very fragmented, but that it has developed into a freestanding entity during the last three years; in the previous years it was basically approached from the perspective of CSR. The analysis suggests that during the next years it will maintain a high degree of interaction with other themes, and thus develop a high degree of importance in this knowledge field.
"What other themes are linked to SRCB research?" (RQ3) The results of the co-word analysis show that the themes linked to general research into SRCB have derived from CSR research. This is very clear in the second period analyzed. In the third period, when SRCB emerged as a freestanding subject, the research revolved around personality traits and citizen consumption.
"How have these themes evolved since 1991?" (RQ4) In general, the evolution map shows strong fragmentation among the SRCB works since its inception and identifies some underlying thematic areas. In this evolutionary structuring of the scientific field, as we have previously noted, works linked to consumer attitude and CSR stand out. In the last period, certain specific themes appear to be addressed to a greater extent (with more than 10 papers). This is the case with knowledge and information in general, ethical consumer, organic products, sociocultural variables, ethical consumption, consumer studies, and specific references to the methodology followed, including the analysis of applied multivariate data.
"What are the most important themes and subject areas in terms of academic output?" (RQ5) If we consider at a global level the production of the thematic areas, measured by number of documents published (see Table A4 in the Appendix A), three main areas should be highlighted: (a) Research on attitude (themes: "attitude", "fair trade"," organic product", and "ethical consumer"), (b) research on CSR (" CSR", "knowledge and information", behavior", "business", and "SRCB"), and (c) research on social and sustainable consumption behavior ("socially responsible consumption behavior", "sustainable consumption behavior", "country and areas", "consumer decision-making", and "methodology").
If this measurement criterion is used again for different themes (see Table A5 in the Appendix A), concepts linked to some of the earlier thematic areas are repeated, such as "attitude", "ethical consumer", and "fair trade", linked to the thematic area of research into attitude, and "behavior", and "CSR", linked to the thematic area of CSR.
As a final reflection, it is good to remember that all transactions have a profound impact on society, which gives the exchanges a social dimension. Their results, therefore, must be evaluated in terms of "fairness" or "justice" for all parts of the market; this is the domain of normative marketing ethics [86]. Thus, through the evaluation of the social impact of consumption, marketing practice and ethics are closely connected.
Environmental and health problems, linked to the production and consumption systems of the most developed economies [87,88], and the effects of potential pandemics (such as the Coronavirus respiratory syndrome, the Zika virus, and the COVID-19 virus declared a pandemic by the WHO in March 2020), are evidence of irresponsible behaviors. These irresponsible behaviors may be transitory, such as an excessive demand for medical (e.g., masks and gloves) and other necessary products (toilet paper and disinfectant), or more structural, and require a change to a more rational and sustainable consumption model.
Identifying the factors and circumstances that determine the behavior of the social and economic agents in the exchange, and ways to raise awareness of the importance of consumers' (who are also voters) behavior, will be essential for the promotion of responsible management and growth. This is the way to achieve the sustainable development goals established by the 2030 Agenda. The Agenda aims to move towards societies with inclusive economic growth, greater social cohesion and justice, living in peace, and with sustainable environmental horizons. This paper aims to contribute to these aims, through the review and analysis of the academic research on socially responsible consumer behavior (SRCB) and related themes, identifying its evolution, trends, and applied perspectives.

Limitations and Future Research
In the present study, we identify key areas in socially responsible consumer behavior research (SRCB), identify the structure of the thematic networks of the research themes in the academic literature, and provide important insights that can shape future research. However, we encountered several difficulties due to the biases inherent in analyses of this type.
First, a particular limitation is that the accuracy of the applied method depends on the thresholds defined as restrictions in the course of data homogenization and extraction of the structure of the sub-domains. The analysis conducted enables discussion about general trends, widely accepted by the scientific community, to be legitimized, as the procedure applied inevitably excludes themes of marginal importance and clarifies interpretation of the findings. Although the authors varied the criteria (upper and lower limits), no significant changes were noted in the conceptual structures; the final solutions to the threshold issues are partially dependent on the technical decisions they took.
The authors suggest that future research, for a more exhaustive study, might extend the analysis by including conference proceedings, trade and professional journals, and by extracting data from other bibliographic databases. In addition, it would be interesting to determine how papers from prestigious research centers and pre-published manuscripts (available online) might stimulate additional SRCB research. Furthermore, the findings suggest that the existing research is not comprehensive, thus indicating that further work is required in each of the identified sub-domains, or streams of research, to gain more insight into crucial aspects of SRCB. This result is not surprising, and it supports the authors' calls for more research aimed at clarifying the theoretical background of this topic, which may still be considered under development.
An interesting future line of research would be to relate the emerging issues in the scientific research identified in the field (such as SRCB) with the key issues in the political and social debate, to examine to what extent there is a harmony and alignment of scientific concerns with social and political concerns.
It is hoped that the ideas put forward in this summary, and the future lines of research suggested, will contribute to advancing the current knowledge and understanding of the academic literature on SRCB.

Conflicts of Interest:
The authors declare no conflict of interest.

Thematic Area Documents
Research on CSR 243 Research on attitude 238 Research on social and sustainable consumption behavior 202 Research on 'Ethos Marketing' 93 Established theory-based approaches 79 Research on sociocultural factors under the auspices of environmental orientation 73 Research on identity and willingness to pay 66 Research on 'green' concern 54 Source: Own illustration. Source: Own illustration.