Employee-Related Disclosure: A Bibliometric Review

: Academic research speciﬁcally focused on employee-related disclosure practices is needed to enhance understanding on CSR reporting. This paper aims to provide an overview of the state-of-the-art in research on employee-related disclosure, analyzing the characteristics of the scientiﬁc production on this topic. A bibliometric analysis is conducted on the papers speciﬁcally focused on employee-related disclosure published from 2000 to 2019 in journals indexed on the Web of Science database. The ﬁndings show that relatively few studies speciﬁcally focused on employee-related disclosure have been published over the last two decades (63 papers). Most articles were published during the last 8 years (93.6%), although the highest interest in the study of employee-related disclosure among scholars concentrates on a short period around 2017. Six journals concentrate 31.75% of the publications on the subject. Most papers are empirical studies, using the content analysis technique to analyze corporate reports. Papers are spread over three research subtopics: (1) extent, quality and drivers of human resource disclosures, (2) occupational health and safety disclosures, human rights disclosures and employee-related disclosures as a legitimization tool, and (3) diversity reporting. In all research subtopics, most of the papers have been published during the last four years, conﬁrming that employee-related disclosure is a topic of current interest to researchers. The studies found that the overall level of employee-related disclosure is low, with an increasing or irregular tendency over time. Furthermore, not all items/categories got the same attention by ﬁrms. It can be concluded that this research subject is still far from reaching the level of research on environmental reporting and important issues remain to be resolved, both theoretically and empirically.


Introduction
Nowadays, Corporate Social Responsibility (CSR) constitutes a key element in firms' corporate agenda worldwide [1]. In essence, CSR posits that firms ought to assume their responsibility towards society, which implies going beyond the search for economic profits and integrating social and environmental concerns in their operations and objectives [2,3]. At the same time, CSR supposes a new way of dealing with a company's stakeholders, in which transparency plays an essential role [4]. In this sense, CSR reporting is the means used by companies to convey information regarding their CSR performance to stakeholders [5].
Although CSR reporting has been extensively studied from both a theoretical and empirical viewpoint over the last decades [6], most research has been focused on environmental reporting and/or the overall set of CSR disclosure dimensions, whereas relatively few studies laid emphasis on employee-related disclosures, analyzing them in isolation [7][8][9][10][11]. Furthermore, issues related to human resources management, such as work environment, occupational health and safety (OHS), work-life balance or diversity and equal opportunities, have been understudied by academic literature [12,13]. This lack Table 1. Search criteria and keywords.
"corporate social respons* report*" or "corporate social respons* disclosure*" or "CSR report*" or "CSR disclosur*" or "sustainability report*" or "sustainability disclosure*" or "social respons* report*" or "social respons* disclosure*" or "social report*" or "social disclosure*" or "labor report*"or "labor disclosure*" or "labor-related report*" or "labor-related disclosure*" or "employee report*"or "employee disclosure" or "employee-related report*" or "employee-related disclosure" or "social performance report*" or "social performance disclosu*" or "human resource report*"or "human resource disclosure" or "human capital report*" or "human capital disclosure" or "human capital information" or "disclosure of human capital" or "diversity report*"or "diversity disclosure*" or "disability report*"or "disability disclosure*" or "human rights report*"or "human rights disclosure" or "accounting for human rights"or "sustainability index*" or "voluntary report*" or "voluntary disclosur*" or "social transparency" or "non-financial information disclosur*" or "non-financial information report*" or "integrated report*" or "annual report" and "human resource management" or "HRM" or "labour practices*" or "corporate social responsibility" or "responsible human resource policies" or "responsible human resource practices" or "responsibility of business to respect human rights" or "corporate responsibility for employees" or "socially responsible policies" or "labor-related CSR" or "labor-related corpor* social resp*" or "International Labour Organisation" or "human rights standards" or "human rights" or "decent work" or "labour rights" or "human development index" or "work environment" or "occupational accidents" or "occupational health and safety" or "workplace diversity" or "gender equality" "gender diversity" or "disability diversity" or "people with disabilit*" or "disability in socially responsible companies" or "categories of human capital" Documents types: all. Time period: 2000-2019. Indexes: SCI-EXPANDED, SSCI, ESCI.
The asterisk (*) is used as a wildcard that represents any other character or string of characters, added to the root of a word allows to find all the derivatives built by adding letters to that root. This search returned 461 works. To ensure quality control, we only consider those works published in peer-reviewed journals [45,47,48]. Thus, we excluded book chapters (11 works), conference papers (67 works), reviews (15 works), and special issue editorials (3 works). Similarly, early access articles (3 works) were excluded to ensure consistency so that the final date of all papers corresponds to the period 2000-2019 (given that in some journals the time elapsed until the final publication of the article is very long).
After applying these filters, the sample was composed of 362 articles, which, in a third phase, were carefully read and separately analyzed by each author to identify the pertinent papers. Thus, each of the authors independently examined the papers and summarized their main characteristics and afterwards the results of this analysis were compared. This procedure allows us to avoid biases and ensure an adequate soundness level [37]. In this analysis, the following criteria were used: -Papers focused on overall social disclosure were excluded, since this study is specifically focused on the employee-related dimension of social disclosure. -Papers related to human rights (e.g., compulsory labor, non-discrimination, right to safe and healthy working conditions, etc.) were included because this topic is related to the rights of companies' human resources. -Papers related to human capital disclosures were included as employees are commonly included in a firm's human capital [7][8][9].
As a result of this analysis, 64 papers were identified. However, one paper was eliminated because it was written in German. Thus, the final sample consists of 63 papers. Although it is a small sample, its size is comparable to that of the samples used in other bibliographic or bibliometric reviews published recently (for example, Cillo et al. [45]-69 papers, Broccardo et al. [49]-21 papers, and Sáez-Martín et al. [31]-69 papers). Figure 1 summarizes the selection process of the papers.
The asterisk (*) is used as a wildcard that represents any other character or string of characters, added to the root of a word allows to find all the derivatives built by adding letters to that root. This search returned 461 works. To ensure quality control, we only consider those works published in peer-reviewed journals [45,47,48]. Thus, we excluded book chapters (11 works), conference papers (67 works), reviews (15 works), and special issue editorials (3 works). Similarly, early access articles (3 works) were excluded to ensure consistency so that the final date of all papers corresponds to the period 2000-2019 (given that in some journals the time elapsed until the final publication of the article is very long).
After applying these filters, the sample was composed of 362 articles, which, in a third phase, were carefully read and separately analyzed by each author to identify the pertinent papers. Thus, each of the authors independently examined the papers and summarized their main characteristics and afterwards the results of this analysis were compared. This procedure allows us to avoid biases and ensure an adequate soundness level [37]. In this analysis, the following criteria were used: -Papers focused on overall social disclosure were excluded, since this study is specifically focused on the employee-related dimension of social disclosure. -Papers related to human rights (e.g., compulsory labor, non-discrimination, right to safe and healthy working conditions, etc.) were included because this topic is related to the rights of companies' human resources. -Papers related to human capital disclosures were included as employees are commonly included in a firm's human capital [7][8][9].
As a result of this analysis, 64 papers were identified. However, one paper was eliminated because it was written in German. Thus, the final sample consists of 63 papers. Although it is a small sample, its size is comparable to that of the samples used in other bibliographic or bibliometric reviews published recently (for example, Cillo et al. [45]-69 papers, Broccardo et al. [49]-21 papers, and Sáez-Martín et al. [31]-69 papers). Figure 1 summarizes the selection process of the papers.

Data Analysis Procedure
VOSviewer version 1.6.15 was used to carry out the analysis of the data. VOSviewer is a software developed by Nees Jan van Eck and Ludo Waltman from the Center for Science and Technology Studies (CWTS) of Leiden University which pays attention to the graphical representation of bibliometric maps in an easy-to-interpret way [50].
Additionally, an analysis of the papers was carried out by synthesizing and critically analyzing their main characteristics (e.g., sample, method, findings, theoretical basis).

Scientific Production on Employee-Related Disclosure
Our analysis shows that relatively few studies specifically focused on employeerelated disclosure have been published over the last two decades, compared to the large number of studies on environmental disclosure and/or CSR disclosure [6]. This evidence confirms prior statements regarding the limited research attention given to employeerelated disclosure in literature (e.g., [7,9,10]). Figure 2 depicts the chronological evolution of the publications on employee-related disclosure over the last two decades. As can be seen, the first papers on the subject were published in 2005. These papers were written by Grosser and Moon [35] (published in Journal of Business Ethics) and Kawashita and colleagues [51] (published in Journal of Occupational Health). The most prolific year was 2017, with 13 published articles, followed by 2018 (12 papers) and 2016 (10 papers).
VOSviewer version 1.6.15 was used to carry out the analysis of the data. VOSviewer is a software developed by Nees Jan van Eck and Ludo Waltman from the Center for Science and Technology Studies (CWTS) of Leiden University which pays attention to the graphical representation of bibliometric maps in an easy-to-interpret way [50].
Additionally, an analysis of the papers was carried out by synthesizing and critically analyzing their main characteristics (e.g., sample, method, findings, theoretical basis).

Scientific Production on Employee-Related Disclosure
Our analysis shows that relatively few studies specifically focused on employee-related disclosure have been published over the last two decades, compared to the large number of studies on environmental disclosure and/or CSR disclosure [6]. This evidence confirms prior statements regarding the limited research attention given to employee-related disclosure in literature (e.g., [7,9,10]). Figure 2 depicts the chronological evolution of the publications on employee-related disclosure over the last two decades. As can be seen, the first papers on the subject were published in 2005. These papers were written by Grosser and Moon [35] (published in Journal of Business Ethics) and Kawashita and colleagues [51] (published in Journal of Occupational Health). The most prolific year was 2017, with 13 published articles, followed by 2018 (12 papers) and 2016 (10 papers). In terms of the temporal evolution of publications on employee-related disclosure, as shown in Figure 2, between 2005 and 2012 there was an irregular trend of some years having no publications (e.g., 2007,2008,2010,2011). From 2014 to 2017 there was a noticeable increase in the number of publications, slightly decreasing in the following years. A potential explanation of this increase can be found in the Directive 2014/95/EU, as well as in the Agenda 2030 and the SDGs, which fostered interest in these issues by both companies and researchers [37].
Most papers were published during the last 8 years (59 papers representing 93.6% of the total published papers), although the highest interest in the study of employee-related disclosure among scholars concentrates on a short period around 2017. Accordingly, it can be said that research interest in this topic is current. Table 2 shows the number of publications per journal. In total, 39 journals published papers specifically focused on employee-related disclosure, 33.33% of them belonging to the category Business, Finance (Accounting). The journals with more articles published In terms of the temporal evolution of publications on employee-related disclosure, as shown in Figure 2, between 2005 and 2012 there was an irregular trend of some years having no publications (e.g., 2007,2008,2010,2011). From 2014 to 2017 there was a noticeable increase in the number of publications, slightly decreasing in the following years. A potential explanation of this increase can be found in the Directive 2014/95/EU, as well as in the Agenda 2030 and the SDGs, which fostered interest in these issues by both companies and researchers [37].
Most papers were published during the last 8 years (59 papers representing 93.6% of the total published papers), although the highest interest in the study of employee-related disclosure among scholars concentrates on a short period around 2017. Accordingly, it can be said that research interest in this topic is current. Table 2 shows the number of publications per journal. In total, 39 journals published papers specifically focused on employee-related disclosure, 33.33% of them belonging to the category Business, Finance (Accounting). The journals with more articles published on the subject are Pacific Business Journal of Business (ESCI), and Social Responsibility Journal (ESCI), with four papers each, followed by Accounting, Auditing & Accountability Journal (JCR), Asian Journal of Accounting and Governance (ESCI), Corporate Social Responsibility & Environmental Management (JCR), and Safety Science (JCR), with 3 papers each. With 20 papers in total, these six journals concentrate 31.75% of the publications on the subject. Ten journals have 2 publications, whereas the remaining 23 journals have only 1 publication. In total, 129 authors were identified. The author with more publications on employeerelated disclosure is F.R. Cahaya (3 papers). There are 21 authors who have two publications, whereas the remaining authors have only published 1 paper on this subject. The number of authors per paper varies between 1 and 7 authors. The average number of authors per paper is 2.41. As shown in Figure 3, it is evident that there are far fewer single authored publications than papers published by multiple authors. Specifically, there are 17 single authored publications, whereas 46 papers were written by multiple authors. This trend towards collaboration between scholars researching on employee-related disclosure is maintained throughout the analyzed period. publications, whereas the remaining authors have only published 1 paper on this subject. The number of authors per paper varies between 1 and 7 authors. The average number of authors per paper is 2.41. As shown in Figure 3, it is evident that there are far fewer single authored publications than papers published by multiple authors. Specifically, there are 17 single authored publications, whereas 46 papers were written by multiple authors. This trend towards collaboration between scholars researching on employee-related disclosure is maintained throughout the analyzed period.  Figure 4 depicts the distribution of the papers on employee-related disclosure per country. In total, we found 28 countries with at least 1 publication. As can be seen, Australia stands out as the country with the highest number of publications on employeerelated disclosure, followed by the UK (8 papers). As noted by Cahaya et al. [10] and Li et al. [21], most published studies on employee-related disclosure focus on developed countries (both Anglo-Saxon countries and European countries, as well as Japan). However, interestingly, there are three developing countries (India, Malaysia, and Indonesia) among the countries with a higher number of publications on employee-related disclosure, which could indicate a growing research concern about working conditions and labor-related human rights in developing countries, characterized by relaxed labor standards and a low-cost workforce [14]. Two plausible explanations of this result could be the increasing number of journals specifically focused on Asian countries' issues indexed on the WoS database (e.g., Asian Journal of Accounting and Governance; Asian Review of Accounting; Asia Pacific Journal of Human Resources; Pacific Business Review International) and the increasing collaboration between scholars from emerging countries and scholars from countries with a well-established research tradition (e.g., [10,52]). On the other hand, Latin America is the region with fewer published papers, with only one paper focused on a country from this region (Brazil)   Figure 4 depicts the distribution of the papers on employee-related disclosure per country. In total, we found 28 countries with at least 1 publication. As can be seen, Australia stands out as the country with the highest number of publications on employeerelated disclosure, followed by the UK (8 papers). As noted by Cahaya et al. [10] and Li et al. [21], most published studies on employee-related disclosure focus on developed countries (both Anglo-Saxon countries and European countries, as well as Japan). However, interestingly, there are three developing countries (India, Malaysia, and Indonesia) among the countries with a higher number of publications on employee-related disclosure, which could indicate a growing research concern about working conditions and labor-related human rights in developing countries, characterized by relaxed labor standards and a low-cost workforce [14]. Two plausible explanations of this result could be the increasing number of journals specifically focused on Asian countries' issues indexed on the WoS database (e.g., Asian Journal of Accounting and Governance; Asian Review of Accounting; Asia Pacific Journal of Human Resources; Pacific Business Review International) and the increasing collaboration between scholars from emerging countries and scholars from countries with a well-established research tradition (e.g., [10,52]). On the other hand, Latin America is the region with fewer published papers, with only one paper focused on a country from this region (Brazil).  Another aspect to note is that there are no Scandinavian countries (i.e., Denmark, Norway, Sweden, Finland, and Iceland) among the countries with a higher number of publications on employee-related disclosure despite the fact that these countries have been pioneers in the development of intellectual capital management and reporting models, and are characterized by being greatly interested in social issues [8]. Likewise, the    Another aspect to note is that there are no Scandinavian countries (i.e., Denmark, Norway, Sweden, Finland, and Iceland) among the countries with a higher number of publications on employee-related disclosure despite the fact that these countries have been pioneers in the development of intellectual capital management and reporting models, and are characterized by being greatly interested in social issues [8]. Likewise, the USA ranks sixth in number of publications on employee-related disclosure, despite the fact that, together with the UK and Canada, the USA has a greater number of journals indexed in WoS database, and is considered one of the most "performant" countries, in terms of papers [53]. In this sense, this limited research attention to employee-related disclosure by US scholars could be a reflection of the scant interest of US firms in this kind of disclosures as prior research has showed [54].

Research Subtopics
The identification of research subtopics implies using the bibliographic coupling analysis, which employs the number of citation couplings to "quantitatively measure the degree of static connection between the two manuscripts" [55] (p. 271). This analysis ponders the total links. It should be noted that 2 out of the 63 publications in the network are not connected to each other, i.e., the papers written by de Roo [56] and Kawashita and colleagues [51]. Thus, the largest set of connected papers consists of 61 publications. Figure 5 depicts the bibliographic coupling analysis of the publications on employee-related disclosure, based on total links. As shown in Figure 5, the bibliographic coupling analysis generated three main clusters (each one represented by a different color: red, green, and blue). In this regard, according to van Eck and Waltman [50] (p. 1062), the "clusters that are located close to each other tend to be strongly related in terms of citations, while clusters that are located further away from each other tend to be less strongly related". Furthermore, "the curved lines between the clusters also reflect the relatedness of clusters, with the thickness of a line representing the number of citations between two clusters" [50] (p. 1063).
Additionally, in purple, we identify two papers carried out by Das [42]) and Frangieh and Yaacoub [57], which were published in the journals Pacific Business Review International and Social Responsibility Journal. Although the fact that two articles address the same topic is not enough to talk about a cluster, it is worth pointing out that both papers analyze human resource disclosures in corporate reports stressing their variety and the associated lack of overall comparability. Specifically, they compare the degree of application of the ILO's labor standards and human resource management practices among companies based on their employee-related disclosures, as well as the characteristics of such disclosures to detect common trends and discrepancies and, consequently, such papers use an international sample.
Sustainability 2021, 13, x 10 of 39 application of the ILO's labor standards and human resource management practices among companies based on their employee-related disclosures, as well as the characteristics of such disclosures to detect common trends and discrepancies and, consequently, such papers use an international sample. For each cluster, we identified the following research subtopics: Cluster 1 (color red)-Extent, quality, and drivers of human resource disclosures: It is made up of 26 papers that analyze the quantity and/or quality of human resource (HR) disclosures in corporate reports and seek to identify the internal and external factors that influence the level/quality of HR disclosure, mainly from a stakeholder perspective. Thus, papers in this cluster assess the status (extent and/or quality) of employee-related disclosure in a country or region, or the association between the level of disclosure and several organizational and institutional characteristics (such as company size, ownership structure, firm strategy, industry affiliation, organizational culture, national legal system, etc.). Research interest in this subtopic could be explained by the influence of prior studies on environmental disclosure, as well as the desire of knowing the actual state-of-art with regard to employee-related disclosure.
Within this cluster, the articles with the most links are those from Tejedo-Romero and Araujo [58], Tejedo-Romero and Araujo [59], Petera and Wagner [60], Bordunos and Kosheleva [61], Alawi and Belfaqih [62] and Alvarez [63]. Furthermore, in this analysis, we verify that Rahman et al.'s [64] article is also strongly linked with the subtopic corresponding to Cluster 2. For each cluster, we identified the following research subtopics: Cluster 1 (color red)-Extent, quality, and drivers of human resource disclosures: It is made up of 26 papers that analyze the quantity and/or quality of human resource (HR) disclosures in corporate reports and seek to identify the internal and external factors that influence the level/quality of HR disclosure, mainly from a stakeholder perspective. Thus, papers in this cluster assess the status (extent and/or quality) of employee-related disclosure in a country or region, or the association between the level of disclosure and several organizational and institutional characteristics (such as company size, ownership structure, firm strategy, industry affiliation, organizational culture, national legal system, etc.). Research interest in this subtopic could be explained by the influence of prior studies on environmental disclosure, as well as the desire of knowing the actual state-of-art with regard to employee-related disclosure.
In total, 19 papers belonging to this cluster were written by multiple authors, whereas there are 7 single authored publications. The authors with more papers published on this subtopic are Tejedo-Romero, Araujo, and Rahman, with 2 papers each. The Pacific Business Review International is the journal with more publications on this subtopic (3 papers), followed by the Business Research Quarterly, Social Responsibility Journal, Asian Review of Accounting, and Asian Journal of Accounting and Governance (with 2 papers each).
The first article on this subtopic was published in 2009, and the year with more publications related to this subtopic was 2017 (7 papers). Almost all of the papers belonging to this cluster were published between 2015 and 2019 (only three papers were published before 2015), and more than a half of them were published during the last three years (2017, 2018, and 2019). Accordingly, it can be said that research interest in this subtopic is very current.
The most analyzed countries in this cluster are India (5 papers), Spain (4 papers), and Australia (3 papers), whereas the authors most involved in this subtopic belong to organizations (universities) from Australia (5 papers), Spain (4 papers), India (4 papers), and Malaysia (4 papers). Table 3 shows the papers belonging to this cluster ordered by total links (i.e., the link between papers), including the journal in which the papers have been published, and the studied country or region.  Cluster 2 (color green)-OHS disclosures, human rights disclosures and employeerelated disclosures as a legitimization tool: It is made up of 23 papers. Overall, this group of papers assesses the extent to which companies disclose information on OHS issues (e.g., policies aimed at achieving a good and safe working environment and the wellbeing of the employees, accidents, injury rates, employees exposed to pollution), as well as human rights (e.g., employment conditions, social protection, avoidance of forced or compulsory work, work-family balance). Furthermore, papers belonging to this cluster analyze voluntary disclosure of employee-related information by companies as a means to maintain/repair legitimacy (e.g., in response to adverse publicity or to incidents) or to send a signal to influence external perceptions about the appropriateness of their human resource management practices.
Research interest in this subtopic could be a response to increasing concerns on working conditions and labor rights in global value chains [14], as well as the relevance acquired by social movements for the promotion of civil rights, equality, and social justice [80]. Similarly, this research line has also been boosted by the interest in knowing the underlying reasons behind employee-related disclosure, in light of the use of CSR disclosure as a tool to improve the image and reputation of companies and the increase in "CSR-washing" practices [81].
Within this cluster, the articles with more links are Vuontisjärvi [8], Kent and Zunker [9], Kent and Zunker [82], Loliwe [39], and Li et al. [21]. In total, 17 papers were written by multiple authors, whereas there are 6 single authored publications. The author with the most papers published on this subtopic is Cahaya, with 3 papers, whereas 14 authors have published 2 papers on this subtopic (Adams, Brown, Dixon, Islam, Kent, Muller-Camen, Nikolaou, Neumann, Parsa, Porter, Searcy, Roper, Tower, and Zunker). The journals that have published more articles belonging to this cluster are Accounting, Auditing & Accountability Journal and Safety Science (both with 3 papers), followed by Australian Accounting Review (2 papers).
As in Cluster 1, almost all of the papers belonging to this cluster were published between 2015 and 2019, and almost half of them were published during the last three years (2017, 2018, and 2019). The year with more publications related to this subtopic was 2016 (5 papers), although the first paper on these issues was published ten years early (in 2006). The most analyzed countries are Australia (5 papers), Indonesia (3 papers) and Finland (3 papers), whereas 5 articles used an international sample. The authors who are more interested in this subtopic belong to organizations from Australia (10 papers), UK (5 papers), and Indonesia (3 papers). Table 4 shows the papers belonging to this cluster ordered by total links, including the journal in which the papers have been published, and the studied country or region.  Cluster 3 (color blue)-Diversity reporting: This cluster consists of 10 articles which analyze voluntary human resource disclosures related to diversity and equal opportunities (e.g., employment of women, minorities, and people with disabilities). Research interest in this subtopic could be a response to increasing social concerns on non-discrimination and equal opportunities, as well as the social movements to advance in the recognition and protection of minority rights.
The oldest paper in the sample belongs to this cluster (i.e., the article written by Grosser and Moon published in 2005 [35]. Again, almost all of the papers in this cluster were published between 2015 and 2019, and most of them were published during the last three years (2017, 2018, and 2019). The year with more publications related to this subtopic was 2018 (3 papers). Furthermore, as in Cluster 2, Australia is the most studied country by the papers belonging to this cluster.
In total, 8 papers were written by multiple authors, whereas there are 2 single authored publications. Williams [93], Maj [43], Oliveira et al. [94], Shimeld et al. [95], and Hossain et al. [96] are the articles with more links within this cluster. The journal Corporate Social Responsibility and Environmental Management stands out in this research subtopic, with 2 publications. Table 5 shows the papers belonging to this cluster ordered by total links, including the journal in which the papers were published, and the studied country or region.   Figure 6 show the temporal evolution of the publications in each cluster. As can be seen, in all clusters most of the papers have been published during the last four years (69.231% in Cluster 1, 65.217% in Cluster 2, and 80% in Cluster 3) and a high percentage of papers have been published in the last three years (69.231% in Cluster 1, 65.217% in Cluster 2, and 80% in Cluster 3). Furthermore, in the case of Cluster 3, half of the articles have been published in the last two years. Thus, it could be said that research interest in all subtopics is very current.
Additionally, when we look at the most recent publications (i.e., those corresponding to 2019), we find that Cluster 1 has 2 articles published in this year (which supposes 7.692% of the total publications in this cluster), Cluster 2 have 3 publications (13.043%) and Cluster 3 have 2 publications (20%).     Figure 7 shows the frequency of the major keywords based on the co-occurrence analysis. The most frequent keywords are CSR (total link strength: 49), human capital (total link strength: 50), annual reports (total link strength: 48), content analysis (total link strength: 40), corporate governance (total link strength: 32), disclosures (total link strength: 32) employee-related disclosure (total link strength: 27), and GRI (total link strength: 23).

Impact of the Published Articles on Employee-Related Disclosure
The influence or impact of the published articles on employee-related disclosure is determined based on citations analysis. As units of analysis, we consider the documents (articles), sources (journals), authors, organizations (authors' affiliation) and countries. Table 7 shows the top 10 articles on employee-related disclosure in terms of number of citations. As can be seen, the most cited article, with 106 citations, was written by

Impact of the Published Articles on Employee-Related Disclosure
The influence or impact of the published articles on employee-related disclosure is determined based on citations analysis. As units of analysis, we consider the documents (articles), sources (journals), authors, organizations (authors' affiliation) and countries. Table 7 shows the top 10 articles on employee-related disclosure in terms of number of citations. As can be seen, the most cited article, with 106 citations, was written by Vuontisjärvi [8] with the title "Corporate social reporting in the European context and human resource disclosures: An analysis of Finnish companies". It was published by Journal of Business Ethics in 2006 and belongs to Cluster 2 (OHS disclosures, human rights disclosures, and employee-related disclosures as a legitimization tool). The following papers in terms of number of citations are those written by Ehnert et al. [23] and Grosser and Moon [35], with 78 and 69 citations, respectively. The first one, published by the International Journal of Human Resources Management, also belongs to Cluster 2 and analyzes the human resource reporting practices by the world's largest companies, whereas the latter belongs to Cluster 3 (Diversity reporting). This paper studies the inclusion of gender equality criteria within CSR reporting, and was published by Journal of Business Ethics.
It is worth pointing out that the number of papers written by multiple authors is significantly greater than the number of single authored articles (8 versus 2), although most of the top 10 papers in terms of number of citations were written by two authors (5 papers). The author Carol A. Adams stands out with two papers which are among the top 10 most cited publications. Two journals stand out with more papers among the top 10 in terms of number of citations: Accounting, Auditing & Accountability Journal (3 papers) and Journal of Business Ethics (2 papers). Furthermore, it should be noted that the two earliest papers of the sample are among the top 10 most cited publications, although there are also three relatively recent articles (published in 2016). Regarding the research subtopics, 80% of the top 10 most cited papers belong to Cluster 2 (OHS disclosures, human rights disclosures and employee-related disclosures as a legitimization tool). Figure 8 depicts the temporal distribution of the top 10 most cited publications as well as their distribution by clusters.
Furthermore, it should be noted that the two earliest papers of the sample are among the top 10 most cited publications, although there are also three relatively recent articles (published in 2016). Regarding the research subtopics, 80% of the top 10 most cited papers belong to Cluster 2 (OHS disclosures, human rights disclosures and employee-related disclosures as a legitimization tool). Figure 8 depicts the temporal distribution of the top 10 most cited publications as well as their distribution by clusters.  [83], and McPhail and Adams [90]. The remaining journals in Table 8 have less than 50 citations (between 13 and 33 citations). Furthermore, it should be noted that the most cited journals have published articles related to Cluster 2.  [83], and McPhail and Adams [90]. The remaining journals in Table 8 have less than 50 citations (between 13 and 33 citations). Furthermore, it should be noted that the most cited journals have published articles related to Cluster 2.  It should be noted that, although Australia is the country with the highest number of published articles on employee-related disclosure (n = 17), the UK has a higher number of cited articles (n = 280). Moreover, interestingly, although Austria and Finland are not among the countries with a large number of publications, the 2 papers produced in each country have been highly cited. Conversely, in spite of the relatively high number of publications on employee-related disclosure in some developing countries, such as Malaysia (5 papers) and Indonesia (3 papers), the number of citations that the articles from these countries have received is not significant. Two plausible reasons could explain this issue. Firstly, the average quality attributed to the papers from such countries, compared to those from leading research countries, such as UK and Australia, can limit their citation by other researchers. Secondly, most papers from these countries were published in journals with less research impact (ESCI), which may have also contributed to the low number of citations that they have received.

Discussion
A brief summary of the main characteristics of the analyzed papers is provided in Appendix A (i.e., theoretical framework, methodology, sample, objective and main findings). As can be seen, most papers are based on empirical studies, whereas only five papers carried out a theoretical analysis or a literature review. Among the empirical studies, most of them use as research methodology the content analysis technique, which confirms that content analysis of corporate reports is the research method preferred by researchers in social and environmental reporting [100]. Overall, this analysis is focused on annual reports (30 papers), followed by the content analysis of CSR/sustainability reports (13 papers), whereas some studies combine the analysis of several corporate reports (annual reports, sustainability/CSR reports, and integrated reports) with information disclosed on companies' websites (7 papers), 1 paper analyzes the management report [69] and 1 paper analyzes disclosures released via LinkedIn [64]. Additionally, two papers carry out a "critical discourse analysis" of annual reports i.e., [86,90]. Interviews and surveys are used to a lesser extent (4 papers). In most studies, the type of indicators used to assess the information related to employees are those contained in the GRI's guidelines/standards e.g., [10,13,18,63], whereas one study uses the ILO's indicators e.g., [42].
Most empirical studies analyze listed firms (29 papers), although some papers focus on top companies according to the Forbes or Fortune lists or the largest companies (15 papers). Other papers analyze companies belonging to specific sectors (e.g., real state, mining, financial, manufacturing) or specific types of firms (e.g., multinationals, CSR leaders). Five papers are focused on banks and financial entities. The majority of papers (45 papers) are focused on a single country, whereas 6 papers analyze two or more countries, and 7 papers adopt an international perspective. Most studies (34 papers) consider data corresponding to one year, whereas 21 papers analyze data from several years. As regards the focus, some studies look at employee-related disclosures in a general way, while others focus on specific topics such as human capital, OHS, human rights, or diversity.
From a theoretical viewpoint, many studies (14 out of 63) are based on a combination of theories commonly used in CSR research (i.e., agency theory, stakeholder theory, legitimacy theory, institutional theory, signaling theory, and agenda setting theory), while most studies rely on a single theory, standing out stakeholder theory (12 papers), followed by institutional theory (7 papers), and legitimacy theory (6 papers). Nevertheless, in the case of papers belonging to Cluster 2, legitimacy theory is the most used theoretical framework. Other theories used by a minority group of papers are critical theory (2 papers belonging to Cluster 2), gender schema theory (2 papers belonging to Cluster 3), resource dependence theory, prospect theory, Marxist feminist theory, social identity theory and social exchange theory (one paper each). Furthermore, several papers lack a theoretical framework (13 out of 63).
As regards the findings, the studies found that the overall level of employee-related disclosure is low, with an increasing or irregular tendency over time. Furthermore, authors observed that not all items/categories got the same attention by firms. As regards disclosure quality, studies also document a low quality level as a consequence of the lack of consistency and comparability of disclosures, the predominance of narrative disclosures, or the bias towards positive/favorable information. Authors attribute this low disclosure quality to the lack of regulation, as well as low stakeholder pressure.
Many studies aimed to identify the determinants or drivers of employee-related disclosures.
In particular, the effect of firm size [23,24,60,64,70,71,87], industry membership [9,17,23,24,52,74,84], government ownership [41,59,70], and board independence [6,41,94] on employee-related disclosures has been analyzed by a high number of studies, which found that such factors are associated with the level or quality of employeerelated disclosures. Moreover, many other factors that influence environmental reporting also have an effect on the extent of employee-related disclosures. In this sense, the potential drivers that have been considered by the studies can be separated into four categories (in order of importance): -Firm-level drivers: this group of factors includes several firm-specific characteristics such as firm size, industry membership, organizational culture, market capitalization, cross-listing, profitability, economic performance, internationalization, and employee power. -Governance-level drivers: this group of factors includes both corporate governance mechanisms and the firm's ownership structure. Among the corporate governance mechanisms, special attention is given to the attributes of the board of directors (e.g., board size, board diversity, board independence, and board activity), whereas the drivers related to the firm's ownership structure include managerial ownership, employee ownership, state ownership, and ownership concentration. -Country-level drivers: refer to institutional pressures at the country level derived from the national government environment, the country's level of economic development, national culture, regulatory context, or the country's level of human rights risks. -Report-level drivers: refer to whether the firm elaborates non-financial reports.
Additionally, some studies analyzed the effect of stakeholder pressures on the level and characteristics of employee-related disclosures. For example, Rahman et al. [64] analyzed the influence of unionization, whereas Kent and Zunker [9,82] and Li et al. [21] studied the influence of the media.

Complementary Analysis
Given the relatively few studies specifically focused on employee-related disclosure that have been published in journals indexed on the WoS database over the last two decades (63 papers), the search was repeated by using the Scopus database. In this case, after applying the same filters that were used in the case of the main analysis, we identified 17 additional papers (Table 9).  16-29. In this case, the Nevertheless, some characteristics of this new group of papers are similar to those of the papers included in the main analysis. The number of papers written by multiple authors is significantly greater than the number of single authored articles (11 versus 6). Most papers are empirical studies (16 out of 17), the majority of which adopt the content analysis of annual reports as research method (9 papers) and are focused on listed firms (9 papers). Most papers analyze a single country (13 papers) whereas 3 papers adopt an international perspective. Specifically, 6 papers focus on developing countries-India (2 papers), Brazil, Indonesia, Sri Lanka, and South Africa (1 paper each)-and 7 papers focus on developed countries-Germany and the UK (2 papers each) and Australia, Spain and Sweden (1 paper each).
Although the bibliographic coupling analysis was not used with these papers, after reading them, 12 papers could be identified with Cluster 1, 4 papers could be identified with Cluster 2, and 1 paper would be related to Cluster 3. Thus, similar to the main analysis, most papers belong to Cluster 1.

Concluding Remarks
In this study, a bibliometric analysis was carried out on the papers specifically focused on employee-related disclosure published from 2000 to 2019 in journals indexed on the WoS database by assessing the impact of authors, journals, countries/regions, organizations and topics, as well as their temporal evolution in order to systematize the existing research.
We found 63 articles specifically focused on employee-related disclosure, most of them published between 2015 and 2019 (80.95%), 2017 being the most prolific year in terms of the number of published papers. Thus, on the one hand, our analysis shows that relatively few studies specifically focused on employee-related disclosure have been published over the last two decades, compared to the large number of studies on environmental disclosure and/or CSR disclosure [6], which confirms prior statements regarding the limited research attention given to employee-related disclosure in literature (e.g., [1,10,11]). However, on the other hand, we have observed a positive trend in terms of growth of the scientific production on this subject and it could be said that research interest in this topic is current.
We also found that the journals that have published more papers on this subject are Pacific Business Review International and Social Responsibility Journal, followed by Accounting, Auditing & Accountability Journal, Asian Journal of Accounting and Governance, Corporate Social Responsibility and Environmental Management and Safety Science. Although a relatively high number of authors have shown interest in employeerelated disclosure, they have not been particularly fruitful, as less than 20% of them have produced more than one paper. Moreover, the number of single authored articles is significantly lower than the number of papers elaborated by multiple authors. F.R. Cahaya is the author with more publications on this subject. Furthermore, Australia is the country that stands out in this research subject.
Bibliographic coupling analysis allowed us to identify three clusters or research subtopics: (1) extent, quality and drivers of human resource disclosures, (2) OHS disclosures, human rights disclosures and employee-related disclosures as a legitimization tool, and (3) diversity reporting. In all clusters, most of the papers have been published during the most recent years of the analyzed period (2016, 2017, 2018 and 2019), confirming that employee-related disclosure is a topic of current interest to researchers. The subtopic with more publications is the first one, although the most cited papers belong to Cluster 2, which ranks second in number of publications.
With regard to the impact of the research, although the majority of the papers were written by multiple authors, the most cited article is a single authored paper written by T. Vuontisjärvi and published in 2006 in Journal of Business Ethics. This journal also has the highest number of citations. Furthermore, the most cited publications were written by authors with affiliation to European organizations.
Additionally, several characteristics of the studies on employee-related disclosure can be highlighted. Most studies are quantitative, using the content analysis technique to analyze corporate reports. Overall, this analysis has been focused on annual reports, CSR/sustainability reports or both. Interviews and surveys are used to a lesser extent. Most empirical studies analyze listed firms from a single country and consider data corresponding to one year. From a theoretical viewpoint, studies on employee-related disclosure have been based on a variety of theories commonly used in CSR research, such as agency, stakeholder, legitimacy, signaling and agenda setting.
In conclusion, we could state that the last five years have witnessed an increase in interest among scholars in studying employee-related disclosure as a specific topic of research. Interest in this subject can be explained by the strategic role of a company's human resources [9,61] and, on the other, it has been stimulated by increasing concerns in working conditions, labor rights and equal opportunities.
However, this research subject is still far from reaching the level of research on environmental reporting and important issues remain to be resolved, both theoretically and empirically. On the one hand, research could be expanded in each of the clusters identified in this study by addressing new issues. Thus, for example, in cluster 1, new organizational and contextual variables could be analyzed by studying their effect both on the overall extent and/or quality of employee-related disclosure and on each of the categories/types of employee disclosures. Similarly, the scope of study in Clusters 2 and 3 could be extended to an international sample instead of focusing on one specific country or region in order to identify trends and drivers of such disclosures. On the other hand, it would be interesting to establish connections among clusters; for example, by identifying under what organizational and contextual characteristics, the employee-related disclosure practices converge/diverge. Furthermore, researchers could also delve more deeply into the effect of employee-related disclosure on the financial and non-financial performance of companies.
To sum up, the growing social awareness in relation to issues related to this subject (for example, employment of women and minorities, social protection, working conditions, etc.) and resulting demands of accountability on companies can promote the development of research in this area [21]. In this sense, by depicting the current status of research on employee-related disclosure, this study's findings provide a reference frame that could guide researchers regarding the direction of future studies on this subject.
This study is not exempt from limitations. We have included only the WoS database as a source of data collection. Other databases, like Google Scholar and Scopus, should also be considered to analyze research on employee-related disclosure. In order to address this limitation, future studies could extend the sample of research articles by selecting more databases to develop comparative studies based on different databases. Future research may also perform a qualitative analysis to bring about more in-depth knowledge about this research area.

Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.

Data Availability Statement:
The data presented in this study are available on request from the corresponding author.

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