Women in top echelon positions and their effects on sustainability: a review, synthesis and future research agenda

This article aims to review and systematize prior works that investigate how the presence of women in top echelon positions of firms affects sustainability and to create an agenda to guide future research in this promising area. In contrast to previous reviews, ours examines how women in top echelon positions affect sustainability by distinguishing both the position women held in the firm (i.e. Board of Directors—BoD, top management team, CEO and relevant committees) and the specific elements of sustainability (i.e. activity, performance, and disclosure). Our structured systematic review resulted in 187 publications retrieved from Web of Science and Scopus and revealed that the presence of women in top echelon positions is associated with greater engagement in social and environmental projects. Their presence also positively influences the environmental and social performance and increases the level, quality, and transparency of sustainability disclosure. Furthermore, the presence of women in top echelon positions and the implementation of sustainable activities improve both the firm financial performance and value. However, conflicting results have also emerged. On the basis of these findings, research gaps and future research agenda are identified and presented.


Introduction
In 1987, the concept of sustainable development, defined as the "development that satisfies the needs of the present generations without compromising the ability of the future ones to fulfill their own needs", was introduced (Sharma & Henriques, 2005;WCED, 1987). Since 1987, sustainability, which refers to the balance 1 3 of social, environmental, and economic criteria in business (e.g. Almeida & Melo, 2017;Khan et al., 2016;Montiel, 2008;Saunila et al., 2019) has received increased attention in managerial practices and academia (e.g. Boyd et al., 2007;Walker et al., 2014). Firms need to meet the growing demands of consumers and stakeholders for sustainable initiatives and more detailed reporting on them (Baumgartner & Ebner, 2010;Johnsen et al., 2017). Given the attention received in management practices, researchers are placing emphasis on understanding how sustainability is pursued and its activities are reported (Walker et al., 2014). As a result, a number of studies analysing this topic have emerged.
At the same time, the role of women in top echelon positions (Brunninge et al., 2007) has gained importance. In this review, the term "women in top echelon positions" is used with the goal of including all relevant positions in the firm that can be held by women. Specifically, in line with Brunninge et al. (2007), by top echelon positions we mean these roles: Board of Directors (BoD), top management team, CEO, and other relevant committees. Specifically, the composition of BoDs has been investigated since it is not only one of the main corporate governance instruments in the supervision of managerial actions, but also the body where decisions are taken on the strategic objectives of firms, including those related to sustainability (Akhmetshin et al. 2018;Ferramosca & Verona, 2020). Instead, the composition of the top management team has been analysed with the aim to understand why organizations act and perform in a certain way (Hambrick, 2007;Hambrick & Mason, 1984).
Capabilities and competencies of people in top echelon positions are, of course, unrelated to gender. However, the gender composition of BoDs and top management teams has widely attracted the attention of researchers and has been studied from numerous perspectives (for a review see e.g. Khatib et al., 2020;Tshetshema & Chan, 2020), being sustainability one of these.
Recent studies have generally found that female directors positively affect firm sustainability and social responsibility, play a key role in ethically managing the sustainable activities of the firm and promote the adoption of ethical policies (see e.g. Gulzar et al., 2019;Nadeem et al., 2017). However, some authors state that board gender diversity has no effect on sustainability (Ajaz et al., 2020) or reduces the participation in sustainable development projects (Loukil et al., 2019). Regarding sustainability performance, several studies find that it is positively affected by board gender diversity (e.g. Elmagrhi et al., 2019;Hafsi & Turgut, 2013;Provasi & Harasheh, 2020;Yaseen et al., 2019). However, other authors find that board gender diversity improves the economic but not the environmental and social dimensions (Reyes Bastidas and Briano-Turrent, 2018). As concerns disclosure, while some studies state that the presence of female directors negatively influences sustainability disclosure (e.g. Fuadah et al., 2018) or does not impact on it (e.g. Dyduch & Krasodomska, 2017;Khan, 2010;Mousa et al., 2018), other studies find positive effects on disclosure (e.g. Anazonwu et al., 2018;Formigoni et al., 2020) and specifically on its level (e.g. Al Fadli et al., 2019;Campanella et al., 2021;Dienes & Velte, 2016;Ullah et al., 2019), quality (e.g. Said et al., 2018) and transparency (Garcia-Torea et al., 2017). Finally, while board gender diversity may increase firm value through sustainability (e.g. Atif et al., 2021;Bektur & Arzova, 2020;Qureshi et al.,
In the literature there are already some reviews and meta-analyses that focus on the effect of corporate governance or BoDs on sustainability and CSR. 1 For example, Naciti et al. (2021) conduct a review that analyses the evolution of corporate governance rules regarding sustainability. Regarding BoD, the review of Rao and Tilt (2016b) examines how its diversity (e.g. in terms of gender, age, nationality, and functional background) affects CSR. Considering CSR reporting, Velte (2017) reviews existing studies to examine how board composition affects its quantity and quality, while the review of García-Sánchez (2020) focuses on how various factors including board composition and its diversity affect CSR disclosure and its external assurance. Regarding gender diversity, the review of Nguyen et al. (2020) examines the effect of female directors on corporate non-financial performance and observes that the majority of analysed studies yield a positive relationship between the two. Finally, in their review Amorelli and García-Sánchez (2020b) investigate how board gender diversity affects firm commitment to sustainability and stakeholder engagement focusing on some CSR dimensions (e.g. sustainability investment and performance), the theoretical frameworks adopted, and the moderating factors of the role of female directors .
Existing meta-analyses show that there is a positive relationship between the presence of female directors and the implementation of sustainable activities (Endrikat et al., 2020), sustainability performance (Byron & Post, 2016), and disclosure (Guerrero-Villegas et al., 2018;Lagasio & Cucari, 2019;Majumder et al., 2017). In addition, the context in which the firm operates plays a role as country-level factors (e.g. institutions) moderate the relationship of female directors on sustainability (Endrikat et al., 2020;Majumder et al., 2017).
In comparison to existing reviews and following the future agenda advanced by Amorelli and García-Sánchez (2020b) who call for further analyses focused on specific elements of CSR, our review goes beyond and investigates how women in top echelon positions affect sustainability by distinguishing both the position women take in the firm (i.e. Board of Directors, top management team, CEO and relevant committees) and the specific elements of sustainability (i.e. activity, performance, and disclosure).
Given the relevance of the topic depicted also by the 2030 Agenda and the 17 Sustainable Development Goals (including gender equality), the contrasting conclusions yielded by previous studies and the limitations of previous literature reviews, this paper identifies and systentizes existing literature on the presence of women in top echelon positions and its effect on sustainability with the purpose to compare and contrast the findings of prior studies. Thus, our literature review provides readers with a state-of-the-art understanding of the research topic, by identifying research gaps and signalling future research avenues.
More in detail, a structured systematic review was performed yielding 187 publications, retrieved through Web of Science and Scopus. Without foreclosing our analysis on any topic and taking an exploratory and deductive approach, our review revealed four main topics of analysis on which women in top echelon positions have an effect: (1) Sustainable activities and strategies (both social engagement and environmental); (2) Sustainability performance (both social and environmental); (3) Sustainability disclosure (level or extent, quality, and transparency); (4) Sustainability effects on firm performance and value (through the moderating role of women in top echelon positions on sustainable activities, performance, and disclosure).
Our review contributes to the academic debate on the issue in three ways. We consider women in all top echelon positions, without restricting the analysis on female directors, as in previous reviews on the topic. We bring clarity and order by offering a novel perspective of existing studies through the identification of four main topics. Furthermore, we contribute to the theoretical advancement by identifying the major research gaps and suggesting future research avenues. These aspects are essential for advancing the study of how the presence of women in top echelon positions affects sustainability.
The remaining part of this paper is structured as follows. In Sect. 2, the methodology used is outlined. Section 3 presents the descriptive statistics of the selected publications and an overview of prior research. Finally, the discussion of managerial and policy implications and future research is outlined in Sect. 4.

Literature review methodology
Based on Tranfield et al. (2003), a structured systematic literature review was performed. For identifying potential sources for reviewing, we select the Web of Science (WoS) and Scopus databases. 2 The search was not subject to publication time criteria and was performed on 1st June 2021.
To identify relevant publications, we first decided the search strings to use. Search strings to be included or excluded in the final search were discussed among the authors with regular meetings; this has helped us overcome the lack of a preliminary "scoping study" that is recommended by Tranfield et al. (2003) with the aim of evaluating the size and relevance of the literature and obtaining objective criteria for delimiting the topic of the review . The final search string was composed by three parts: the first focuses on female presence using female* OR wom*n OR gender; the second focuses on the role of women using bod OR board 1 3 Women in top echelon positions and their effects on… OR corporate AND governance OR manager* OR management; the third focuses on sustainability using sustainab* OR CSR OR corporate AND social AND responsibility. We preferred to use very general terms so as to conduct a research that would remain broad and open-ended. Explaining the themes of analysis in the keywords would in fact have generated limitations in the research.
Search strings had to be contained in the title, abstract and keywords. 3 The studies selected in this way needed to relate to one of these areas: Business, Business Finance, Economics, Environmental Science, and Management. Furthermore, the search was carried out with inclusion criteria (i.e. both quantitative and qualitative studies) and exclusion criteria (i.e. publications whose abstract is not written in English, public media like editorials) (Tshetshema and Kai-Ying Chan, 2020).
For this review, the concepts of sustainability and corporate social responsibility (CSR) must be distinguished. Sustainability refers to the balance of social, environmental, and economic criteria in business, while CSR "encompasses the economic, legal, ethical, and discretionary expectations that society has of organizations at a given point in time" (Carroll, 1979). However, according to Montiel (2008), these two concepts are converging because of "their shared environmental and social concern (…) despite their paradigmatic differences". For this reason, in our literature review, the term sustainability, as defined by WCED (1987) is preferred and adopted.
The following information was extracted from the selected publications: 1. Bibliographic reference (author, year of publication, journal); 2. Gender-related findings, gender effect and topic; 3. Type of female involvement (i.e. Board of Directors, top management team, CEO and relevant committees); 4. Lens theory (i.e. theoretical approach); 5. Methodology (e.g. qualitative, quantitative) and data (e.g. cross-sectional, panel data); 6. Sample characteristics (sample size, firm characteristics 4 ); 7. Year and country of analysis.
The search in Web of Science and Scopus yielded 902 and 329 publications, respectively. From the combination of the two databases, carried out in order to eliminate duplicates, an initial set of 1169 publications was obtained. Following Moher et al. (2009), the publications were first filtered by reading the title and abstract. If this analysis did not lead to a final decision regarding inclusion, the whole text was 1 3 read and analysed. We used our knowledge, judgment and experience many times for deciding upon clear selection criteria (i.e. exclusion/inclusion) of publications in our sample. After exclusions based on abstract and an evaluation based on full text evaluation, we obtained the final set of 187 publications (see Fig. 1). Then, a black-box approach was used to conceptualise the relationship between the presence of women in top echelon positions and sustainability (Mengis, 2020). Specifically, to identify the main thematic results, we adopted an inductive approach. The inductive analysis "refers to approaches that primarily use detailed readings of raw data to derive concepts, themes, or a model through interpretations made from the raw data by an evaluator or researcher" (Thomas, 2006). We therefore allow our thematic themes to emerge from the analysis of the raw data (i.e. a careful reading of the selected publications), without imposing restrictions and having a priori expectations (Thomas, 2006). We categorized the sample literature based on the explicit construct addressed by each study. In doing this, any intermediate factors (e.g. control variables) were ignored because this research is specifically interested in the direct effects of female presence under various contextual conditions. The final categorization of the publications into the emerging themes was reached through discussions among the authors.

Results of the review
In this section, we first offer a discussion of the main methodological and empirical issues. Then we elaborate the topics that emerged from our review of the literature into the thematic results by considering theoretical and empirical findings on female presence in top echelon positions and the effect on sustainability. We outline the selected publications in the Appendix.

Bibliographic reference (author, year of publication, journal)
As Fig. 2 shows, literature on sustainability has grown exponentially since 2010.
The list of journals that published at least two of the selected publications is reported in Table 1. Corporate Social Responsibility and Environmental Management, Sustainability, and Business Strategy and the Environment published the most studies (31, 22, and 19, respectively), indicating a concentration in these three journals of 38% of the selected publications. Instead, there are 55 journals with only one selected publication each on gender and sustainability.

Type of female involvement (e.g. board of directors, top management team, CEO and relevant committees)
160 studies analyse the role of female directors (e.g. Guping et al., 2020;Pucheta-Martinez and Gallego-Alvarez, 2019;Rao & Tilt, 2016a); 24 examine the presence of female managers (e.g. J. Graafland, 2020;Lu et al., 2020aLu et al., , 2020b; 13 consider  Kabongo et al., 2013;Przychodzen et al., 2018); instead only two studies focus on women in the audit committee (i.e. Appuhami & Tashakor, 2017;Bravo & Reguera-Alvarado, 2018) while only one on women in the CSR committee (Elmaghrabi, 2021). 5 Therefore, it emerges the greater attention paid to the role of female directors, which may be linked to the ease with which the data necessary for analysis can be obtained.

Lens theory
Several theories have been used in the field, however our literature review reveals seven main theoretical approaches that guided past research, based on the management literature. As can be seen from  The gender-specific approaches include only two frameworks dedicated and originated as gender studies: the Critical mass theory (17 studies) and the Gender socialization theory (9 studies). What emerges is that most of the theories used in the selected publications to explain and frame gender issues are frameworks for explaining behavior based on values humans place on social group membership, but are not born and declined specifically for gender issues (i.e. social categorization theory, social identity theory, relational demography theory, self-construal theory). They all refer to social perception that can generate prejudice, which is then used as an explanation of gender issues. Theories that are not gender-specific are then the most employed. Finally, we also found theories that look at heterogeneity but are not born and declined specifically for gender issues (i.e. diversity theory and complexity theory). These are theoretical approaches that, unlike social frameworks, emphasize the positive aspects generated by diversity/heterogeneity. All these theories, both gender specific and non specific ones, are applied regardless of the position of women.
In total, 51 different theoretical perspectives are explicitly employed on this topic. Finally, there are 34 studies that do not explicitly rely on any theory.
3.1.4 Methodology (e.g. qualitative, quantitative) and data (e.g. cross-sectional, panel data) The reviewed studies are mainly based on quantitative methods, with the exception of two qualitative studies (Cuadrado-Ballesteros et al., 2017;Rao & Tilt, 2020) and two studies that adopted a mixed method approach (Dwekat et al., 2020;Mahmood et al., 2018). The empirical studies apply a wide range of regression methods including, among others: ordinary least squares, probit, logit, ordered, binomial, 2SLS, generalized method of moments, fixed effects regressions, and structural equation model. Of the 183 quantitative studies, the majority of studies use cross-sectional data, while some employ panel data or longitudinal design (e.g. Fahad & Rahman, 2020;Ramon-Llorens et al., 2021;Shahbaz et al., 2020;Uyar et al., 2020). This review highlights, therefore, a lack of conceptual and qualitative studies on the way the presence of women in firms affects sustainability.

Sample characteristics (sample size, firm characteristics) and year and country of analysis
Our review highlights that the subject of analysis is generally medium to large publicly listed firms (e.g. Arayssi et al., 2020;Kilincarslan et al., 2020;Rejeb, 2017;Zahid et al., 2020), with three exceptions that examined small and medium enterprises (i.e. Courrent et al., 2016;Graafland, 2020;Sancho et al., 2017). Fifty-five studies use multi country data (e.g. García-Sánchez et al., 2020b;Valls Martínez et al., 2020), of which 9 studies focusing only on European contexts (e.g. Ben Fatma & Chouaibi, 2021; Gangi et al., 2021;Nuber & Velte, 2021). 132 studies analyse the data of only one country; the most considered countries are geographically distributed and include: United States (26 studies), China (15 studies), Australia (12 studies), Spain (11 studies), Malaysia (7 studies), United Kingdom (7 studies), France (7 studies), Bangladesh (6 studies), Pakistan (5 studies), Italy (5 studies), Canada (4 studies). This degree of internationality is perhaps not surprising given the fact that sustainability is crucially important in many economies around the world (Amorelli and García-Sánchez, 2020a). However, there are a number of important regions where research in gender and sustainability is underrepresented in the journal literature, including Eastern Europe, Africa, Latin America, and Asia, despite the importance of these regions to understanding the role of female presence in different contexts (Khan et al., 2019a(Khan et al., , 2019b.

Thematic results
Following the procedure described in Sect. 2, the influence of women in top echelon positions on sustainability was categorized with reference to these topics: (1) sustainable activities and strategies, (2) sustainability performance, (3) sustainability disclosure, (4) sustainability effects on firm performance and value. As regards topic 4, we should specify that under this label we consider the effect that one or more sustainability dimensions (i.e. sustainable activities and strategies, sustainability performance, sustainability disclosure) have on the firm performance and value. The emergence of the four issues is consistent with the terms used in the meta-analyses on the topic that were identified and set forth in the introduction.

Sustainable strategy and activities
Seventy-nine studies investigate the relationship between gender in top echelon positions and sustainable activities, of which 50 find a positive relationship, 4 a negative relationship, 14 mixed results and 11 no relationship. Almost all analysed studies examine the effects of the presence of women on sustainable activities by distinguishing according to their position.
Many studies reveal a positive relationship between the presence of female directors and sustainable activities (see e.g. Beji et al., 2020;Rehman et al., 2020;Saheed Olanrewaju et al., 2020). Female directors not only positively affect corporate sustainability, but they also play a key role in "enabling firms to ethically manage their social responsibilities and sustainable practices" (Yasser et al., 2017) and in promoting the adoption of equality, diversity and inclusion policies (Bruna et al., 2014). While having a positive effect on CSR, female directors also decrease corporate social irresponsibility (Boukattaya & Omri, 2021). Arayssi et al. (2016) state that the presence of female directors "favourably influences on a firm's risk and performance through promoting a firm's investment in effectual social engagements and reporting on them". Female directors facilitate the use of the firm's scarce resources towards social projects that maximize value (Jizi, 2017) and encourage the firm's affiliation with the United Nations Global Compact (Martínez-Ferrero et al., 2020). 6 In the case of banks, those with more female members on their boards incline toward socially responsible behaviour, especially in greater regulatory and stronger investor protection environments (García- . Gender diversity increases sustainability expenditure of banks (Hosain, 2020) while it decreases their energy usage (Fakoya and Nakeng, 2019). On the contrary, Gallego-Sosa et al. (2020) find no significant differences between banks' commitment to the planet on the basis of board gender diversity.

3
Women in top echelon positions and their effects on… The educational background, talent, and experience of female directors is important in the adoption of sustainable environmental initiatives (García Martín & Herrero, 2020): therefore the presence of talented women in the firm allows them to manage social responsibility and sustainable practices in an appropriate way (Setó-Pamies, 2015).
On the contrary, Loukil et al. (2019) state that "the presence of female independent directors reduces firm involvement in sustainable development projects". Instead, some studies find that board gender diversity has no effect on sustainability (e.g. Ajaz et al., 2020;Ardito et al., 2020;Zaid et al., 2020). Finally, other studies find mixed results. For example, it results that female directors are beneficial for sustainability engagement only if they are not members of the controlling family, while they foster philanthropic engagement only if they are members of the controlling family (Campopiano et al., 2019). According to Cullinan et al. (2019), while female independent directors are positively associated with sustainability, this is not true for female executive directors.
While Yarram and Adapa (2021) observe that gender diversity positively influences total sustainability but not its individual components, other studies find that female directors influence both environmental and social sustainable activities.
Regarding environmental sustainability, many studies find that female directors are positively related to attitudes towards environmental protection (e.g. Cosma et al., 2021), the pursuit of environmentally friendly strategies (Glass et al., 2016), carbon reduction initiatives (Haque, 2017), corporate environmental investment (Hu & Yang, 2021), and a higher probability that the firm takes part in sustainabilitythemed alliances (Post et al., 2015). 7 Environmental sustainability initiatives are positively influenced by gender diversity, in both demographic (i.e. the percentage of women on the BoD or in top management positions) and structural terms (i.e. firm policies and practices that enable or reinforce gender diversity) (Kassinis et al., 2016). According to Shoham et al. (2017), firms increase their involvement in environmental sustainability as soon as they appoint a woman to the BoD; however, this decision is strongly influenced by the culture of the countries in which the organization operates (Xie et al., 2020). Moreover, the likelihood of a firm to create pollution is moderated by the positive relationship between the presence of female directors and the environmental policy of the firm . All these positive effects of female directors on environmental sustainability can explain the choice of majority family owners and dual-class owners to appoint female directors with the charge to advance "their personal preferences for environmental corporate social responsibility" (Cordeiro et al., 2020).
On the contrary, Galbreath (2011) highlights that despite the important role of women in sustainable activities, it could happen that due to sex-based biases and stereotyping, men directors ignore the suggestions from female directors on aspects regarding environmental quality with the consequence that female directors are not significantly associated with environmental quality. Wei et al. (2017) specify that when there are only one or two female directors on the board, no significant relationship on environmental investment can be seen; however, when the number of female directors reaches at least three, they have a significantly positive effect on it but only in state-owned firms and firms from heavily-polluting industries.
Moving to social activities, the presence of female directors (as well as in top and middle management) has a positive effect on sustainable activities with gender equality objectives (Larrieta-Rubín de Celis et al., 2015).
The effect of gender diverse boards on sustainability dimensions varies depending on the type of stakeholder: this diversity positively affects sustainability dimensions that are associated with stakeholders with less power (e.g. the environment, contractors, and the community), but it does not affect sustainability dimensions that are related to stakeholders with more institutionalized power (e.g. employees and customers) (Francoeur et al., 2019). In the interaction with various stakeholders, female directors are able to talk with them and to satisfy their needs, reducing the risk of their negative reactions, which can damage firm profits (Galbreath, 2011).
Finally, female participation on BoDs has an effect on specific aspects. Together with board independence, board gender composition affects sustainable supply chain responsibility through three channels: CEO duality, sustainability committee, and sensitive industries (Benjamin et al., 2019).
Focusing on female managers, conflicting results emerge. According to some studies, environmental and social commitments are greater for female managers (Buil-Fabrega et al., 2017). Female managers positively affect "corporate sustainable competitive advantage, which included both the inhibiting effect on unethical environmental behavior and the stimulating effect on proactive environmental strategies" (Pan et al., 2020). Moreover, compared to men, female managers tend to implement diversity and labor flexibility policies related to work schedule and flexible work as part of their sustainability (Arredondo Trapero et al., 2013). On the contrary, according to Q. Lu et al., (2020aLu et al., ( , 2020b, the relationship between the presence of female top managers and sustainability is negative especially for firms in a market with a low marketization level. Instead, some studies find that the presence of women on the top management team does not affect sustainability practices (e.g. Prudêncio et al., 2021), both regarding sustainability as a whole or each of its dimensions (economic, social and environmental) (Martínez León et al., 2011). More in detail, Courrent et al. (2016) show how manager characteristics like gender, age, experience, and training do not influence a firm's pursuit of social activities, while their personal values (measured using ethics and local territorial belonging) do influence these activities. For example, in the purchase of products, it seems that on average, purchasing managers are willing to pay a premium for products that are compliant with the United Nations Global Compact; this willingness is not affected by the gender of the purchasing managers (Goebel et al., 2018). Finally, mixed results were found by Wu et al. (2019), according to which while existing female executives or top managers stimulate corporate philanthropy (and this relationship is influenced by the firm controller and the degree of industry competition), they do not affect the scale of philanthropy.
Regarding female CEOs, Galbreath and Tisch (2020) find that women in the operations manager role foster environmentally sustainable practices, while women in the CEO role do not. However, when women are in both CEO and operations manager roles in the same firm, the relationship with environmentally sustainable practices is positive.
If we analyse the relationship between the presence of women and sustainable activities and strategies considering the role they play, it emerges that the literature is almost unanimous in stating that female directors have a positive effect on sustainable activities. Conversely, when analyzing the position as manager, the results are mixed, perhaps due to the small number of studies. One common finding from the analyses on the effect of women in the two positions (i.e. in BoD or top management team) is that the results are positively influenced by the demographic, educational, and cultural characteristics of the women (Courrent et al., 2016;Kassinis et al., 2016;Xie et al., 2020). Instead, too few studies are related to the CEO and other committee positions to draw conclusions.

Sustainability performance
Fifty studies investigate the relationship between women in top echelon positions and sustainability performance, of which 37 find a positive relationship, 2 a negative relationship, 7 mixed results and 4 no relationship. Of course, the environmental and social performance depends on various factors (Fig. 3). First of all, strategies regarding sustainability play a key role: "firms with more effective CSR strategies exhibit better environmental and social performance" (Orazalin & Baydauletov, 2020). However, sustainability performance also depends on both BoD characteristics (e.g. size, independency, diversity, and activity) and corporate characteristics (e.g. firm size, leverage, and growth opportunities), which, when properly combined, lead to high levels of social responsibility performance (Cuadrado-Ballesteros et al., 2017). Biswas et al. (2018) confirm this result, finding that "firms with higher board gender composition, greater board independence and sustainability committees tend to have better social and environmental performance". Furthermore, even board gender diversity alone positively affects the sustainability performance as confirmed by several studies (e.g. Chams and Garcia-Blandon, 2019; Govindan et al., 2021;Lu & Herremans, 2019;Romano et al., 2020;Uyar et al., 2021). The positive relationship between female directors and sustainability performance is higher when there are female chairs within the board CSR committee (Eberhardt-Toth, 2017) and when the firm has a consumer market orientation (Hyun et al., 2016) or operates in a maledominated industry (Zaichkowsky, 2014) or has an environmental and social risk exposure (Naveed et al., 2021).
Other studies find opposite results. Specifically, Fakir and Jusoh (2020) and García-  find no relationship between female directors and sustainability performance. Two studies demonstrate a return on investment in sustainable activities decreasing with the proportion of female directors (Bristy et al., 2020;Zhuang et al., 2018). Finally, mixed results are found by for example Alazzani et al. (2019) and Ardito et al. (2020). Zhang (2012) finds that while there is a positive relationship between board gender diversity and institutional strength and technical strength of sustainability, the relationship is not significant when considering the weakness ratings of sustainability performance.
Some studies consider the environmental and social performance achieved by firms. While these two aspects of sustainability are usually pursued together, it could happen that one aspect is more important than the other due to the influence of culture and institutional context. For example, the Malaysian culture drives firms to place more importance on the social performance strictly linked to human orientation than on other dimensions (e.g. economic, environmental and marketplace aspects) (Alazzani et al., 2017). Considering both the environmental and social performance, Shaukat et al. (2016) find that the board gender diversity enables a more proactive and comprehensive sustainability strategy, thus leading to a higher environmental and social performance. On the contrary, according to Reyes Bastidas and Briano-Turrent (2018) female directors (or CEOs) positively affect the economic dimension, but worsen the environmental and social dimensions.
Focusing on environmental performance, some studies find a positive relationship between female directors and environmental performance (e.g. Lopatta et al., 2020;Orazalin & Mahmood, 2021). As anticipated in the previous section, the participation in sustainability-themed alliances, associated with a high representation of women on the BoD, positively affect the corporate environmental performance (Post et al., 2015). 8 Considering both sustainability strategy and environmental performance, Orazalin and Baydauletov (2020) find that the positive relationship between these two aspects is negatively affected by the board gender diversity. Finally, Nadeem et al. (2020) and Nguyen et al. (2021) find no relationship between female directors and environmental performance.
Considering the social performance, while according to Landry et al. (2016) female directors increases the probability of the firm to appear on lists measuring ethics or organizational quality (e.g. the Most Admired Companies, the Most Ethical Companies, the Best Companies to Work for, and the Best Corporate Citizens), according to Sanan (2016) there is no significant association between gender diversity of boards and social performance.
A greater gender balance in top-management increases sustainability performance (McGuinness et al., 2017). Female managers also positively affect the firm's environmental performance with the "development of eco-friendly products and commitment to resource reduction" (Burkhardt et al., 2020). On the contrary,  find that a U-shaped relationship between female managers and sustainability performance exists.
Regarding female CEOs, it was found that they positively affect sustainability performance (Huang, 2013). This positive effect is evident both in polluting and non-polluting firms, which are able to significantly reduce pollutant emissions (Jiang & Akbar, 2018).

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Women in top echelon positions and their effects on… If we analyse the effect of women on sustainability performance considering the role they play, it emerges how female directors lead to mixed results in this case. Specifically, the role of women in other committees emerges in this regard. On the other hand, if one analyses the position as manager, the results are mostly in agreement in detecting positive effects. Also in this case, there exist too few studies in relation to the position of CEO to draw considerations.

Sustainability disclosure
The presence of women in top echelon positions also has an effect on sustainability disclosure through "documents intended to inform all stakeholders of the economic, social and environmental impacts of corporate performance, with respect to a given period of time" (García- Sánchez et al., 2019). Seventy-seven studies investigate this relationship, of which 55 find a positive relationship, 5 a negative relationship, 8 mixed results and 9 no relationship.
The presence and number of female directors positively affects firm's disclosure (e.g. Alia & Mardawi, 2021;Frias-Aceituno et al., 2013;Girón et al., 2020;Peng et al., 2021). Several aspects are positively affected: the level or extent of disclosure (e.g. Issa & Fang, 2019;Ong & Djajadikerta, 2018), its quality (e.g. Khan, Khan, & Senturk, 2019a, 2019bMahmood & Orazalin, 2017;Vitolla et al., 2020), its transparency (Garcia-Torea et al., 2017), its lower risk of impression management strategies (i.e. the risk that these reports are a "result of opportunistic behaviour, by which managers can disclose biased information"; García- Sánchez et al., 2019). Finally, female participation on BoDs is among the factors that predict the engagement of firms in the assurance regarding sustainability disclosure, which is recognized as a means to increase its reliability, and that affect the choice of the provider with a preference towards auditing professionists (Buertey, 2021;Liao et al., 2018). On the contrary, some studies state that the presence of female directors negatively influences sustainability disclosure (e.g. Cucari et al., 2018; Gallego-Alvarez and Pucheta-Martinez, 2020b) or does not have any effect on it (Giannarakis, 2014;Giannarakis et al., 2014;Yusoff et al., 2019). Finally, other studies find mixed results: according to Biswas et al. (2021) female directors who are affiliated to the governing family, founders and other board members reduce disclosure in family firms; instead, unaffiliated female directors enhance disclosure both in family and non-family firms.
According to critical mass theory (Dahlerup, 2006), the number of female directors that produces significant effects on firm's disclosure is identified as at least three by for example De Masi et al. (2021). In this regard, Alazzani et al. (2017) suggest that the (insufficient) number of female directors considered in their analysis may have led to the conclusion that there is a "moderate relationship between board gender diversity and CSR disclosure". Instead, according to Manita et al. (2018), even when the critical mass (three female directors) is reached, no significant relationship between board gender diversity and sustainability disclosure is found.
Regarding the quality of disclosure, García-Sánchez et al. (2019) state that female directors produce "more balanced, comparable and reliable information", even if at the same time they are associated with "less precise and clear information, given their narrative character"; these effects are larger in more stakeholder-oriented countries. Al-Shaer and Zaman (2016) specify that when female directors are independent, the quality of sustainability reporting is amplified with respect to the presence of non-independent female directors. However, Amorelli and García-Sánchez (2020a) highlight that the positive role of women on voluntary information disclosure does not remain when they become CEO: in fact, when they reach this position, female directors start to adopt a "a male stereotype regarding voluntary information disclosure", regardless of the human capital of the directors.
Focusing on environmental disclosure, there is a positive relationship between the presence of female directors and environmental disclosure (Rao et al., 2012;Yusoff et al., 2016), including the likelihood of disclosing information regarding climate change (Ararat & Sayedy, 2019;Ben-Amar et al., 2017), carbon (Hossain et al., 2017), corporate greenhouse gas emissions (Hollindale et al., 2019;Tingbani et al., 2020). 9 The board gender diversity is among the factors that determines the quality of environmental disclosure (Baalouch et al., 2019). On the contrary, according to Kılıç and Kuzey (2019), the presence of female directors is not associated with the carbon disclosure index and the decision of a firm to respond to the Carbon Disclosure Project. A similar result is found by Post et al. (2011), according to which reaching this critical mass does not affect the disclosed environmental corporate social responsibility.
Regarding the effect of female managers, Dilling and Caykoylu (2019) find a significant negative correlation between integrated report quality and the ratio of female executives. 10 Gender diversity in the audit committee characteristics has a significant positive influence on the level of CSR disclosure and on the CSR environmental disclosure (Appuhami & Tashakor, 2017). It also increases the quality of voluntary sustainability reporting both in terms of comprehensiveness and relevance, as women may operate as monitoring mechanisms in the increasing commitment to provide valuable sustainability information and to display greater stakeholder orientation (Bravo and Reguera-Alvarado, 2018). 11 If we analyse the role of women on sustainability disclosure considering the position they held, it emerges that the literature is almost unanimous in stating that female directors have a positive effect on sustainability disclosure albeit with due 9 The positive effect of female directors on environmental disclosure has also been found in the case of banks. Specifically, Gallego-Alvarez and Pucheta-Martinez (2020a) find that female directors of banks encourage the reporting of environmental information in countries with coordinated market economies. 10 Regarding other entities, Garde  observe that the gender of the manager in state owned enterprises is not statistically significant in influencing the disclosure of CSR information. In the case of banks, Prabowo et al. (2017) find that the presence of female executives positively affects CSR disclosure, especially in banks listed on the stock market. The effect of female managers is observed only in medium and larger banks and in banks without government ownership (Prabowo et al., 2017). 11 Some studies also consider the effects that female directors produce on the sustainability disclosure of particular entities. For example, according to Tapver et al. (2020), the positive association between the proportion of women on the board and sustainability disclosure also exists in the case of banks. In the case of state-owned enterprises, when female directors are the majority, it seems (i.e. there are weak indications) that the total sustainability information disclosed decreases (Argento et al., 2019). specification. This relationship is, in fact, the most analysed in the literature and, therefore, the most exhaustive and articulated in describing how the characteristics of the board enter into the relationship. The same considerations apply to the committees that in this case are more investigated. Therefore, a similar relationship emerges between women in the BoD and relevant committees and sustainability disclosure. Viceversa, if one considers the position as manager, the results are mixed, perhaps, once again, due to the small number of studies.

Sustainability effects on firm performance and value
Only 15 studies analyse the relationship between the presence of women in top echelon positions (in which they moderate sustainable activities, performance, and disclosure) and the financial performance of the firm and its value. Of these studies, 9 find a positive relationship, 2 a negative relationship, 3 mixed results and one no relationship. 12 Among others, Chong et al. (2018) highlight the need of firms to "engage in sustainable development to maximise the firms' value" and stress the essential role of women in defining the strategy regarding these activities.
Board gender diversity can increase firm value by promoting renewable energy consumption (Atif et al., 2021) or by promoting sustainability disclosure (Bektur & Arzova, 2020). In fact, sustainable activities will be appreciated by the stakeholders and lead to "more beneficial contracting and opening new avenues of growth" , which will be valued on the market and result in higher stock prices. In this mechanism, board gender diversity is extremely important, as firms with higher diversity tend to disclose more regarding sustainable activities, as exposed in the previous section. Furthermore, Arayssi et al. (2016) demonstrate that the presence of female directors "favorably influences on a firm's risk and performance through promoting a firm's investment in effectual social engagements and reporting on them".
Contrasting results are reported in few studies. Ajaz et al. (2020) state that there is a negative relationship between board gender diversity, sustainability performance and a firm's financial performance, while there is no significant relationship with the firm's reputation. Bristy et al. (2020) demonstrate that the return on investment in sustainable activities decreases with the proportion of female directors.
In the case of managers, it has been found that gender diversity in top management teams increases the level of implementation of sustainability, with an effect on firm performance (Quintana-García et al., 2018).
Female CEOs and CFOs also have a positive effect on firm performance through the promotion of sustainability. The appointment of a chief executive in the area of sustainability can improve the financial performance, as the "company shows its commitment to sustainability and social responsibility to its stakeholders" and this positive image "may have signaling effects for its customers, employees, and shareholders" (Wiengarten et al., 2017). The greatest benefits can be obtained if this female executive has a background in functions related to sustainability (Wiengarten et al., 2017) and is an independent director rather than a male executive director (Atif et al., 2020).
Female CFOs also improve firm performance such as debt cost saving as they conduct more environmentally responsible activities, whose effects are more prominent in high risk firms (Wang et al., 2021).
It is difficult to analyse the effect of women in top echelon positions on firm performance and value considering the role they play, given the small number of studies. However, it seems to emerge that the effect tends to be positive regardless of position in the Bod, top management team, as CEO or in relevant committees. Table 3 is a summary table showing the effect that women in the various positions held in the firm (BoD, managers, CEO) are able to exert on the various dimensions of sustainability (i.e. sustainable activities and strategies; sustainability performance; sustainability disclosure; sustainability effects on firm performance and value). As can be observed, most studies identify a positive relationship between women and sustainability: women, whatever position they hold in the firm, have a positive effect on sustainability, whether measured by sustainable activities and strategies, sustainability performance, sustainability disclosure, or sustainability effects on firm performance and value.

Women in top echelon positions
The relationships between women in the BoD and the four sustainability topics are not only the most numerous, but they are also those studied paying more attention to other aspects besides the gender variable. Specifically, regardless of the relationship analysed, socio-demographic and educational (e.g. García Martín & Herrero, 2020), cultural (e.g. Alazzani et al., 2017), institutional (e.g. García-Sánchez et al., 2019), firm (e.g. Hyun et al., 2016;Naveed et al., 2021), and industry (e.g. Zaichkowsky, 2014) factors were also considered in the analysis. Specific cases relating to particular sectors (e.g. food sector as in García-Sánchez et al., 2020a;oil, gas and mining as in Saheed Olanrewaju et al., 2020); logistics as in Govindan et al., 2021; electronics and chemical as in Post et al., 2011) and specific types of business (e.g. family firms as in Campopiano et al., 2019) were also explored in this report. Probably, as already mentioned, such attention and scientific production is also due to the greater availability of data.

Concluding remarks
A subject advances when prior studies are logically synthesized based on their findings (Kumar et al., 2020). After doing this, we developed a comprehensive future research agenda with reference to methodology and empirical issues, theory constructs, and thematic issues. Before revealing the agenda, we present managerial and policy implications.

Managerial and policy implications
The analysis revealed that generally the presence of women, whatever position they hold in the firm, is associated with a greater engagement in social and environmental projects  Furthermore, findings suggest that policymakers should consider the presence of women on the BoD when designing laws affecting environmental and social sustainability and when deciding whether to participate in private firms. As both gender diversity and/or the presence of a critical mass in top echelon positions may foster sustainability, policy makers should implement specific actions to stimulate such a virtuous relationship.

Methodological and empirical issues
Our discussion of the main methodological and theoretical findings on female presence in top echelon positions and sustainability allowed us to identify some important gaps that can be analysed in future research. A summary is offered in Table 4.

Suggestion 1
Despite the fact that many studies have considered the relationship between women in top echelon positions and social and/or environmental sustainability, there is no unified theory behind the commitment to sustainability. We argue that the theoretical support for the possible link between gender in top echelon positions and sustainability comes from the two most prominent theories and a specific gender theory: Stakeholder theory (as for sustainability), Upper echelons theory (as for characteristics of BoD and/or top management teams) and Gender socialization theory (as for gender).

Suggestion 2
Our review highlights a lack of conceptual and theoretical studies on the way the presence of women in firms affects sustainability. Only two studies employed a qualitative approach and two a mixed method. For these reasons, the first item on our agenda aims to assess how the inclusion of both qualitative (e.g. interviews, case studies and longitudinal studies) and a mixed methods design will improve our understanding of the interplay between gender and sustainability. Usually, the analysis of both phenomena is performed using quantitative methods because data collection is usually indirect. However, this can limit understanding of the interplay we seek to explore (Creswell & Plano Clark, 2018). For example, only with qualitative studies it would be possible to investigate in more detail how women influence two relevant aspects: the decision making process of BoD that leads or not to the pursuing of sustainability in the firm; and the implementation of sustainable activity and disclosure with its effects. As a consequence, the combination of quantitative statistical trends and in-depth understanding given by qualitative research techniques can create a stronger research methodology than a single approach (Bryman, 2008).

Suggestion 3
The analysis of the effect of women on sustainability considering some top echelon positions they hold is scarce. Specifically, while the studies about the BoD are proliferating since 2010, almost scarce are the ones analysing the top management team, CEO and relevant committees. We argue that there is a need to better understand the influence of the demographic, educational, and cultural characteristics of the women in these unexplored specific positions. Currently, too few studies are related to the relevant committee as CEO and in relevant committees to draw conclusions.

Suggestion 4
Although it is people in top echelon positions that generally strongly influence the decisions of a firm and their implementation, it may be interesting to examine how women in other positions (particularly staff level female workers) influence the sustainability of the firm. To the best of our knowledge, no study has focused on the effect of women in non-top echelon positions on firm sustainability. Female workers, together with male workers, may play a key role in the execution of sustainable activities decided at higher firm levels, with a significant effect on the performance of these activities (on the contrary, they have no effect on disclosure, which remains the sole responsibility of the higher bodies). The influence of the lower corporate levels on sustainable activities may be particularly relevant in smaller organisations with a less hierarchical structure, in which employees are more empowered, responsible and autonomous, as they can directly propose solutions and ideas, take decisions, and solve firm issues. For this reason, it is possible that the best ideas, which are then implemented, come from the most skilled workers that are not on the BoD or top management teams.

Suggestion 5
There are a number of important regions where research in gender and sustainability is underrepresented in the literature; as such we suggest exploring the contexts of: Eastern Europe, Africa, Latin America, and Asia. We believe that analysing the influence of women in top echelon positions in different contexts could advance the field given that country-level factors (e.g. institutions) moderate the effect of female directors on sustainability (Endrikat et al., 2020;Majumder et al., 2017). Furthermore, the analysed samples are almost exclusively representative of medium and big listed firms. We suggest further analysis considering firm heterogeneity, and specifically that related to governance and size, which can help shed further light on the issue. Both the dimension (smaller firms) and the ownership structure (family concentrated or not) should be taken into account as they both represent more than 80% of world wide firms (Family Firm Institute, 2020).

Thematic issues
The framework used to reveal the emerging findings allowed the identification of some important topics that should be analysed in future research. A summary is offered in Table 4.

Suggestion 6
Among the four identified thematic issues (i.e. sustainable activities and strategies, sustainability performance, sustainability disclosure), the effect that women have on firm performance and value is underexplored. In fact, the majority of studies (126 out of 187) examine the effect of women only on sustainable activities or disclosure, without assessing the effect on performance. Instead, 61 studies estimate achieved performance (either at the sustainability or firm level), but only 15 assess how women, through sustainability, effect on performance at the firm level. This is surprising because if on the one side sustainability is a central issue, on the other one performance and continuous growth is the main goal of every firm (Goyal et al., 2013). Today, it is more correct to talk about sustainable growth as sustainability is the only viable way to continue doing business in the coming decades. Therefore, our suggestion is to further analyse the relationship between the presence of women in top echelon positions, sustainability and firm performance and value.

Suggestion 7
Among the four topics, there is not a dominant controversial theme. However, each of the thematic results confirm a non-unanimously-positive effect of the presence of women in top echelon positions. This is particularly true when analysing the roles women play. Therefore, we suggest deepening the topics concerning sustainable activities and strategies, sustainability performance, sustain-ability impact on the firm performance and value by considering the specific role of women in the top management team, CEO and relevant committees.

Suggestion 8
With regard to sustainable activities, it would be interesting to examine through which activities the firm seeks to achieve superior sustainability performance. Specifically, innovation can play a key role in achieving this goal (Lopatta et al., 2020;Nadeem et al., 2020). For example, in the case of environmental sustainability, it could be interesting to understand to what extent the presence of women in the firm increases innovation aimed at obtaining less polluting finished products or at producing with a lower environmental impact (i.e. by acting on the productive aspect). The implications of these changes on the firm's environmental performance should then be examined.

Suggestion 9
BoDs and top management teams play a critical role in implementing sustainable activities and policies and their gender composition may have important consequences on that (Kabir & Thai, 2021;Yasser et al., 2017). For example, Nielsen and Huse (2010) note that "women may be particularly sensitive to-and may exercise influence on-decisions pertaining to certain organizational practices, such as corporate social responsibility and environmental politics". In addition to gender, the institutional context should be considered as it has a prominent role in shaping both individual differences in personality traits (Wood and Eagly, 2002) and individual perceptions of others. We argue that other studies are needed in order to understand the different possible effects of women in top echelon positions on sustainability, for example by comparing egalitarian versus male oriented contexts. Indeed, just a few studies analysed the effects of a stereotypical view within the organization on sustainability (e.g. Galbreath, 2011). We suggest considering the social constructs of gender in different institutional contexts (i.e. egalitarian versus non-egalitarian) and how stereotyped views may affect their attitude toward sustainability. This suggestion is particularly important when studying the presence and therefore the role of women according to their position.

Suggestion 10
In the analysis of sustainability disclosure, future research should consider the context to a greater extent. Specifically, since the laws that require firms to provide information on non-economic aspects differ among countries and in different contexts and given that firms may disclose non-economic information for different reasons, it may be interesting to understand how the presence of women in top echelon positions influences sustainability disclosure by comparing the level of disclosure required by law and that offered by firms (Fernandes et al., 2018). In fact, existing studies (e.g. Fernandez-Feijoo et al., 2014) consider only the presence or absence of laws of this kind, but not the level of disclosure that they require of firms. It could also be interesting to analyse the reasons and factors underlying the emerging higher levels of disclosure provided by firms (de Villiers & Dimes, 2021) in comparison to that required by law.