Gender quotas: an interdisciplinary scoping review

Gender quotas have proliferated worldwide as a major tool of gender equality policies, first in the electoral arena and then expanding to other socioeconomic spheres, notably corporate boards. The ensuing rich body of scientific literature on gender quotas so far remains split across disciplines, with a main partition between political science and economics. This scoping review aims at fostering an interdisciplinary dialogue between research on gender quotas conducted from different disciplinary and methodological perspectives. To this effect, we compiled an original bibliographical database of 379 peer-reviewed articles, which we coded according to a series of variables including discipline, geographical area, quota domain, methodology and research question. Drawing on this database, this scoping review presents an overview of the main research questions and findings regarding the genesis and the impact of this policy tool, and offers ideas for the further development of interdisciplinary quota research.


Introduction
Gender quotas are increasingly used as a public policy tool to address gender inequality. Over the past decades, they were first widely enacted in the electoral sphere and have been expanded to other socioeconomic spheres, particularly corporate boards, but also higher education, sports or trade unions. Gender quotas most often mandate that a minimum percentage of women be named in the instances to which they apply. These policies can take various forms: they vary in size (the share of women they require), some include placement mandates such as zipper systems (particularly quotas for elections using proportional representation), and sanctions for non-compliance widely vary from voluntary quotas to mandated quotas imposing more or less strict sanctions.
This policy tool has been characterised by its worldwide spread since the 1990s. The first nationally legislated electoral quota was enacted in 1991 in Argentina and many other countries followed suit in the 2000s and well into the 2010s. In 2022, ninety-seven countries across all continents had national-level legal provisions to increase women's representation in elected offices-of which seventy had implemented quotas and twenty-seven reserved seats-according to the IDEA Gender Quotas database 1 which provides more details about country-specific legislation including quota type and size. Gender quotas on corporate boards are more recent and less widespread: in 2006, Norway became the first country to introduce a substantial quota requiring that there be at least 40% of women on the boards of public and state-owned companies. Over the past few years, several countries, such as Belgium, France, India, Italy or Pakistan, have implemented similar legislation. Even though more and more organisations are issuing recommendations for gender quotas on corporate boards, they have yet to become the norm since they often remain conditional to individual companies' willingness to implement them.
The diffusion of quotas has attracted the attention of many scholars. Mirroring the policy's spread from political representation to corporate boards, the subject was firstly and overwhelmingly tackled in political science before becoming of interest to management and economics. Research on gender quotas, however, remains very compartmentalised as only a limited number of studies compare quotas across spheres. This scoping review aims at bridging these so far largely separate bodies of the literature in view of a broader evaluation of gender quotas as a policy tool: why are quotas adopted in different spheres? How are they implemented, and with what effects on gender inequalities? We argue that an interdisciplinary approach, taking into account the inputs of a diversity of disciplines (addressing different questions, and using different methods leading to complementary findings) leads to a more comprehensive evaluation of how quotas function and the change they bring about.
To this effect, we have compiled and made publicly available online 2 a database of 379 references of peer-reviewed academic articles on gender quotas in all their domains of application, produced by scholars of diverse disciplines. Based on descriptive statistics and a qualitative analysis of this database, we offer a systematic and interdisciplinary scoping review of gender quotas as a public policy tool. To our knowledge, this is the first paper of its sort considering that, thus far, 17 out of the 18 literature reviews published in peer-reviewed journals that we have identified in our bibliographical search focus on a single quota domain. The only article-based review encompassing both types of quotas dates back to 2017 and includes a more limited number of references (Hughes et al. 2017). Our more recent literature search enables us to take into account the sharp increase in the volume of quota literature since the mid-2010s. Our approach also opens a broader dialogue with policy evaluation.
This article is structured around four parts. In the first section, we present our methodology: the search protocol and the selection criteria that we applied to the construction of our sample and database, along with an explanation of the coding of variables and a brief description of our sample. The next two sections offer a comprehensive and comparative overview of the literature's methods and results, organised around the two main research questions that arise, that is the genesis and the effects of gender quotas. Finally, we discuss the state of the existing literature and identify avenues for future research.

Methodology and corpus overview
This scoping review is based on the analysis of 379 peer-reviewed journal articles written in French and English that were gathered through several bibliographical searches on interdisciplinary scholarly databases. The main body of the literature was collected through searches executed in 2019 on the Scopus database and in 2020 on the dimensions database through search strings associating keywords such as "women", "gender" and "sex" with "quota(s)" (Figs.1, 2, 3 and 4). 3 All the references hence gathered were compiled into a charting table with ten main variables describing articles' metadata and focus. These notably include: geographical scope, quota domain, research question, method used and academic discipline. More detailed variables were created for parts of the corpus in order to systematise the analysis. For example, for all the articles dealing with the effects of quotas, a variable was created to categorise the criteria used to evaluate quota impact, and another to characterise the overall effect assessed by the study.
Working on the aggregated level of this charting table facilitates an overview of the general characteristics of gender quota literature. It was mainly developed as of the 2000s (only 14 articles were published before 2003), with a sharp increase in academic publications since the mid-2010s. A large majority of the references (70.82%) look into electoral gender quotas, even though an increasing share of articles (19.63%) discusses gender quotas on corporate boards (see Fig. 1). This difference is most likely linked to the chronology of gender quota implementation. As a corollary, in terms of academic disciplines, political scientists have initially been most prolific (63.93%). Recent studies, however, come from increasingly diverse disciplines, notably management (27%) and economics (12.5%) (Fig. 4).
In terms of geographical focus (Fig. 2), in spite of a large concentration in Western Europe, all continents are covered by the literature. About a third of the empirically-based articles include international comparisons. Amongst these comparative articles, 34 (30%) compare two-to-six cases and 79 (70%) deliver regional or worldwide comparisons-of the former, 19 exclusively focus on cases from the global North and 15 on cases of the global South.
In terms of research questions (Fig. 3), a majority of publications (63.66%) looks into the effects of gender quotas, most of which aim to assess quota efficiency using quantitative methods. The second most common question relates to the genesis of quota policies (19.36%), with a preponderance of papers using qualitative methods in this category. The questions of quotas' effects and genesis are simultaneously addressed only by a handful of articles (2.39%). The third most common question concerns attitudes towards quotas (5.31%) and is mostly addressed using survey data.
This vast body of literature is generally organised around two main research questions, focusing, respectively, on the genesis and on the effects of gender quotas. In what follows, we summarise the main methods and conclusions of the reviewed literature on these two questions. In an effort for conciseness, we only punctually point to examples of references (for a more detailed presentation see (Revillard and Tuffy 2022)).

The genesis of gender quotas
In our sample of articles looking into the genesis of gender quotas (N = 73), qualitative approaches and case-studies are vastly dominant. Nonetheless, international comparisons based on various methods and conceptual approaches make up a substantial part of the literature. Though they only concern seven articles, it is noteworthy that history-modelling techniques have been increasingly used in recent years to understand the spread of quotas worldwide. Finally, discursive analyses have contributed to casting light upon the logics at play in the enactment of quotas in different countries and across domains. Electoral quotas are the main focus of investigation. Most of the literature looking into their genesis seeks to identify the factors that enhance the chances of quota adoption-and a few articles look into cases of non-adoption. This large body of literature adds to and nuances Mona Lena Krook's framework identifying four main explanations for the adoption of gender quotas: demands for quotas from women's movements, the support of political elites who may see some strategic advantage in supporting quotas, the adequacy of quotas with conceptions of equality and representation, and the influence of international norms (M.L. Krook 2007).

Women's movements
Militancy in favour of gender quotas, be it within the electoral sphere or in non-partisan settings, is often the first step for quota adoption. Several case-studies as well as a handful of cross-national quantitative studies cast light upon the relationship between policy changes and women's involvement in politics, both in and out of the partisan sphere. The presence of women in the highest ranks of a party is significantly correlated with in-party support for gender quotas and, subsequently, the adoption of party quotas (ex. Caul 2001). Furthermore, cross-partisan mobilisation of women legislators in favour of quotas raises the cost of opposing the policy and hence facilitates its adoption. Local women's movements have been identified as the most important determinant for quota adoption (ex. Kang and Tripp 2018), notably since they can help overcome strong partisan divides that paralyse the debate. The success of non-partisan mobilisations, however, depends on their internal cohesion. Reciprocally, failure to adopt gender quotas is often linked to the lack of a strong and united women's movement (see for example in Japan (Gaunder 2015)). While a key determinant of quota adoption, women's mobilisations interact with other structural and conjunctural factors.

Political environment
As regime type shapes local politics, it can influence the likelihood of quota adoption considering the varying weight that is given to international norms and the space given to both quota advocates and detractors. Democratic institutions do not necessarily favour their adoption (Bauer and Burnet 2013) as legal quotas indeed face resistance by political parties questioning their democratic character. These concerns may be lifted with courts' validation of affirmative action (Piscopo 2016). In developing countries, democracy may even weaken incentives to buckle under international pressures pushing for the implementation of gender quotas (Randall 2006). At the party level, an internal democratic organisation is thought to favour the adoption of a quota.
A reformative context initiated by demands for better representation and the subsequent consultation of civil society have offered a propitious environment for the adoption of gender quotas (Meier 2012). Likewise, quota advocacy has been successful in post-conflict contexts where electoral laws, if not political regimes, were undergoing profound transformations, with gender equality sometimes becoming a pillar of post-conflict reconstruction.
There is a rather broad consensus in the literature that a competitive electoral setting increases parties' incentives to support and apply gender quotas, especially at the party level. For leftist parties usually, adopting quotas can be a strategy to attract more women voters when their electoral success is threatened by another, ideologically close, party. In a context where party and legal quotas are already enacted and electoral competitiveness is strong, the two types of quotas may mutually reinforce each other as parties constantly seek to surpass their competition.
Considering that decision-making bodies are systematically dominated by men before the enactment of quotas, their adoption may seem paradoxical: why would men support a policy that could jeopardise their ascendency over elected offices? Gender quotas may, in fact, be seen as a political opportunity for men (Opello 2007). Game theorists have argued that men's support for gender quotas can be rational and self-interested depending on electoral rules: for example, in single-member constituencies, quotas would heighten men's chances of running against a woman and, therefore, of winning a constituency (Fréchette et al. 2008). Moreover, quota adoption can be explained by "party pragmatism" in light of ideological, electoral and strategic incentives thus weighing actors' trade-offs besides the policy's sole direct effects (Murray et al. 2012).
Political inclination can affect individuals' and parties' propensity to support quotas, as well as the logic that may eventually guide the adoption of a quota. Left-wing parties have usually been precursors in a concern for improved political representation, whilst right-wing parties have most often adopted quotas after they became an international norm.

Quota diffusion and contagion
International organisations have set new normative expectations in the past decades regarding the adoption of measures to redress gender inequality, and particularly of electoral gender quotas. The rapid and worldwide diffusion of quotas in the 1990s and early 2000s largely owes to international influence exerted over national quota policies, resulting in a "norm cascade" whose mechanisms and effects differ according to structural and conjunctural factors (Swiss and Fallon 2017). Quotas have become one of the tenants defining state modernity. They are hence used as "signalling devices" to demonstrate commitment to democracy (Edgell 2017) as is often the case for countries receiving international aid.
International quota debates can also emulate local debates as illustrated by the two successive waves of quota adoption in Latin America (Piatti-Crocker 2019) and the influence of the European Union's parity debate on opening up the debate in its member states (MacRae 2012). Finally, international NGOs promoting affirmative action for women have also played a significant role, albeit in contexts where a larger programme for gender equality was already in place.
The enactment of a gender quota in one instance may facilitate and/or encourage the adoption of quotas in other parties or at the country level through a logic of contagion (Petra Meier 2005). Besides holding leftist values and having women in highranking positions, the previous adoption of a gender quota by a party heightens the likeliness of quota adoption by another. Moreover, parties that have already adopted an internal quota may play a crucial role in the adoption of a similar measure at the national level (Verge 2012).

Policy formulation and design
Policy formulation inevitably influences its outcomes; hence, a clear definition of a gender quota's goal is an important condition to its efficacy. A smaller portion of the literature concerned with the genesis of gender quotas and that is mostly based on discursive analysis looks into the meanings that are given to gender quotas and their implications for implementation.
Debates over gender quotas-that may have led to their adoption or notreveal different conceptions of political representation. A common denominator in quota advocates' discourse consists in redefining a group's underrepresentation as a collective rather than an individual issue. As such, the core values defining a country's model of citizenship can affect the likeliness of it adopting any form of gender quota (Mona Lena Krook et al. 2009). For example, India adopted a gender quota very early on, but it later faced much opposition. Initial quota enactment was in fact instrumental to strengthening colonial rule, as it was used to legitimise existing political institutions rather than to promote women's representation (Dutoya 2016). Discursive shifts can also lead to policy changes after the initial enactment of a quota as was the case in several Latin American countries that replaced quotas with parity laws: gender balance became a prerequisite for democracy and was hence integrated as a permanent measure (Piscopo 2016).
Gender quotas legally divide the population into two mutually exclusive groups: women and men. As their design needs be rather straightforward, it supposes that each of these groups is relatively homogenous and they hence run the risk of producing essentialising legal effects as they are formally oblivious to other social hierarchies (Mansbridge 2005). Reframing the policy problem that is tackled could curb some of these negative side-effects by producing a normative shift: Rainbow Murray argues that rather than addressing the underrepresentation of women, hence suggesting a shortfall on their part, gender quotas should tackle the overrepresentation of men in decision-making instances (Murray 2014).
Quotas as an equality policy tool may also be directed towards other segments of populations whose underrepresentation is linked to distinctive characteristics: 15 articles compare gender quotas to quotas or reserved seats for racial or ethnic minorities. As is the case with comparison across domains, comparison between quotas targeting different populations, currently rare in the literature, provides fertile ground to assess their use as a policy tool to fight inequality.

The genesis of board and other non-electoral quotas
The literature on non-electoral gender quotas is much more limited, and mainly concerns corporate boards. Dynamics of gender quota enactment can be linked to a "diffusion" (Teigen 2012) or "contagion" (Petra Meier 2005) effect operating at several levels: from an individual organisation to another, from a country or region to another, from the electoral to the corporate sphere. Economic, social or political conjunctures may also play a part in the adoption of gender quotas for they may influence how the problem is framed, and hence the solution that is envisaged. Taking the case of Iceland, Axelsdóttir and Einarsdóttir (2017) argue that the implementation of quotas on boards followed the framing of their use as a solution to the economic crisis. As such, quotas are not considered as intrinsically necessary nor good, but as a palliative to economic decline.

Analysing quota impact
The literature on the effects of gender quotas is composed of a majority (65%) of quantitative studies, drawing on a diversity of methods. A variety of experimental and quasi-experimental methods have notably been implemented in this area, including natural experiments, difference-in-difference and regression discontinuity methods. In what follows, before turning to the analysis of the impact of electoral and board quotas, we first offer a focus on a distinct body of literature on attitudes towards quotas, which includes (but is not limited to) laboratory experiments. These are treated separately since, in practice, they can be implemented in countries with or without quotas (in the latter case, in a more prospective manner).

Attitudes towards quotas
Before the development of quota research per se, research in social psychology had investigated attitudes towards affirmative action-particularly. Twenty articles in our sample tackle the question of general attitudes towards quotas. Proportionally, it is more often addressed in the literature on board quotas (7/74, 9.46%) than on electoral quotas (10/267, 3.74%). These mainly quantitative studies most often explore attitudes in the general public. Nonetheless, some studies focus on specific groups-notably those directly or indirectly impacted by the quota under studysuch as managers, politicians and political parties or higher civil servants. While women tend to be more supportive of quotas than men, perceptions of causes of gender inequality also matter: people endorsing structural rather than individual explanations for gender inequalities tend to be more supportive of quotas (Einarsdóttir et al. 2020). Other determinants include political orientation and political values, as well as institutional performance (good governance) (ex. Beauregard 2018). Citizens tend to be more favourable to quotas in the most interventionist as well as in the most egalitarian countries (Möhring and Teney 2020). Support for quotas, however, should not be conflated with support for gender equality: "benevolent sexism" offers a pro-quota rationale on the basis of women being in need of protection (Katrine Beauregard and Sheppard 2020). Reciprocally, quotas may have a reinforcing effect on gender stereotypes, leading to a perception of female beneficiaries as more "communal" unless "agentic" (Faniko et al. 2017).

Electoral quota impact
Four main criteria stand out in the literature on electoral quota impact: descriptive, symbolic, substantive and sustainable representation.
In turn to the assessment of quotas' impact on descriptive representation, criteria may differ according to the quota type, its interactions with other elements of the political system, the degree of parties' involvement in the quota framework, etc. However, evaluations tend to be generally positive, with quotas described as increasingly efficient in terms of descriptive representation (Högström 2016).
Beyond their sole effectiveness in terms of the number of women elected to office, several studies also look into the impact of quotas on the individual characteristics of candidates and/or elected officials-often in terms of professional skills. Other research has also evidenced that quotas encourage profile diversity in terms of personal, political and professional trajectories (ex. Aldrich and Daniel 2019). Gender quotas, however, seem to have limited effects on age diversity, particularly concerning the election of younger women (Stockemer and Sundström 2020).
The conjunction of gender quotas with ethnic quotas can also lead to greater proportions of ethnic minority women being elected as compared to ethnic minority men. This effect is likely the result of parties' "double-duty" strategy, favouring candidates who fulfil more than one quota at once (Celis et al. 2014). The differentiated effects of gender quotas on the election of women belonging to different groups foment intersectional approaches highlighting the necessity of considering women as a heterogeneous group crossed by multiple dynamics of power (Lépinard 2013).
Beyond descriptive representation, several authors study the broader impact of quotas on inequalities in the political sphere. The diagnoses established by these authors are more or less connected to the notion of symbolic representation-for example, when quota impact is assessed in terms of greater "respect" gained by women (Burnet 2011). While the adoption of quotas has favoured the creation of legislative women's caucuses in various parliaments, women elected through quotas or reserved seats may be granted less respect and authority in plenary parliamentary debates. In some cases, like that of Kenya, quota design has amplified inequalities amongst women in the electoral sphere and quota implementation was met with stronger patriarchal backlash as more women entered the electoral arena (Berry, Bouka and Kamuru 2020).
The effects of gender quotas in terms of symbolic representation thus contrast with evaluations considering descriptive and substantive forms of representation that tend to put forward more positive results. Outside of elite politics, however, quotas seem to have had a positive effect on general attitudes towards women as political leaders, especially amongst women (Allen and Cutts 2018). Beyond the political sphere, quotas can also be evaluated in terms of their impact on gender stereotypes and attitudes towards women more broadly (Clayton 2018). Relatedly, several studies look into the effects of quotas on various dimensions of political participation, be it electoral participation, running for elected positions, or political participation at large (involvement in diverse forms of political activities). Based on a study of 18 European countries, Beauregard contends that the implementation of quotas has reduced the gender gap in political participation by encouraging women's participation (K. Beauregard 2017).
While measures of descriptive representation can be quite straightforward, measuring substantive representation is vastly puzzling. Researchers embarking on this venture have developed various indicators to approximate women's substantive representation: women's participation in parliamentary agenda definition and legislative outcomes (enactment of women's rights laws), the share of time spent discussing women's interests in parliamentary debate, constituency service provision to women, government spending on public health as opposed to other policy priorities, or the integration of social justice issues on party platforms. These studies mostly provide positive assessments of quota impact.
Some contradictory mechanisms may, however, be at play regarding quotas' effects on women's substantive representation. While elected women may feel a mandate to push policies favouring women's rights and interests, they may also be deterred to do so considering the stigma they face as "quota women" (Franceschet and Piscopo 2008). Nonetheless, in an analysis of cross-sectional data from 139 countries, Clayton and Zetterberg identify a "quota shock". They argue that sudden increases in women's descriptive representation tend to induce increases in health spendings and, in parallel, decreases in military spendings (Clayton and Zetterberg 2018).
Some studies explore the possibility of a spillover effect according to which quotas can positively affect the election of women beyond their perimeter of application, for example, from quota tiers to non-quota tiers, from reserved to non-reserved seats. At the interface between the notion of spillover effect and the transformation of inequalities in the political sphere, several studies tackle the question of elected women's promotion and possibilities of access to leadership positions, with limited results notably in the case of France (Lassébie 2020).
Most research evaluates the impact of quotas at a given point in time, but it should also be assessed in the long run. The notion of "sustainable representation" has been coined to account for the durable effects of quotas (Engeli and Mazur 2018).

Evaluating the effects of quotas on corporate boards
The impact of board quotas has been much more investigated than their adoptionwith 51 articles as opposed to 7 on adoption out of 74 articles on board quotas. This body of literature has mostly been developed by scholars of economics and management.
Interestingly, the criteria used to assess the impact of board quotas rapidly expand beyond the immediate goal of the quota, which is to increase the number of women on boards (which would be the equivalent of descriptive representation in the electoral sphere). This dimension is not systematically investigated considering that, in many cases under study, the quota is mandatory and hence presumed to be immediately effective in this regard. However, it is important to stress that, regardless of the domain in which they are implemented, quotas are not necessarily self-fulfilling. As for other gender equality policy tools, their effectiveness in terms of encouraging women's access to corporate boards depends on several of their characteristics, and the ways in which they are implemented (Engeli and Mazur 2018).
As for electoral quotas, the type of board quota regulation at play influences its impact in terms of increased presence of women on boards. The introduction of board quotas has had a stronger effect on the share of women on boards in France and Italy where they are mandatory, as opposed to the UK where they are merely advisory (Bennouri et al. 2020). Firms' characteristics may also influence quota impact. Quotas also tend to be more respected in countries with overall low gender inequality and in firms with strong social consciousness (Clark et al. 2019).
Some studies look into the impact of quotas on the characteristics of board members, notably on the presence of dependent or independent members (Loukil, Yousfi and Yerbanga 2019). Some evaluations focus on women's experiences on corporate boards. While yielding fast results, quotas may also exert pressure on women who are propelled onto boards and often have limited access to top board positions (Rebérioux and Roudaut 2017). This effect, however, seems to tame after the measure has settled and more women have gained experience and promote other women's access to top leading positions (Wang and Kelan 2013). Nonetheless, women on boards report feeling less included and holding less influence over board decisions than their male counterparts (Storvik and Gulbrandsen 2016).
Other studies, however, identify more positive effects, in terms of "challenging gendered ideas of suitability" (Seierstad et al. 2020), and fostering women's access to relevant professional networks (Burzynska and Contreras 2020). Spillover effects may derive from quota adoption as it may affect the firms' standards and board appointment practices beyond the quota's sole scope of application. Empirical tests of this hypothesis provide mixed and even contradictory results. A "quota silo" phenomenon has been described in Norway: as the quota only applies to particular firms, some have changed status to avoid having to comply (Seierstad et al. 2020). Conversely, in France, the proportion of women in corporate boards had increased prior to the corporate quota law of 2011, following the 2008 constitutional reform promoting gender equality (Singh et al. 2015), hence suggesting that a policy environment favourable to quotas can have an impact on women's appointment to boards.
Research on board quotas mirrors that on electoral quotas in that it intends to measure substantive outcomes of the quota besides the increase in the share of women. While the latter focuses on quotas' effects on policy making and thus on forms of substantive representation, the former mostly considers their effects on firms' performance. This criterion is used in 16 out of 51 articles in our sample. This concern for performance mirrors how justifications for quotas are framed in policy making, such as in EU directives. These evaluations often lead to mitigated, if not negative assessments of quota impact (ex. Comi et al. 2020).
Other research shows that firms under the quota regime tend to conduct fewer labour force reductions (Matsa and Miller 2013), and be more focused on corporate sustainability and ethical scores (Provasi and Harasheh 2020). In the face of generally mitigated results, however, it is important to reassert gender equality as a rights issue beyond the "business case" (Humbert et al. 2019).

Discussion
Gender quota research represents a very dynamic and interdisciplinary body of literature. Given the worldwide diffusion of gender quotas as a policy tool, notably in the electoral sphere, this literature is very international-though less so in the case of board quotas which are concentrated in European countries. This body of research draws on a rich diversity of methods, from case-studies to experimental and quasiexperimental designs. The implementation of quotas in different domains, paired with the development of new data streams and data analysis methods, substantially enlarges the set of natural experiments and empirical material that are available to social scientists. The literature is highly comparative: about a third of the articles consider two or more countries in their empirical analysis. Amongst them, more than two thirds (69.91%) include regional or worldwide comparisons, nearly half of which were global (49.37%); the other half either consider countries of the global North (31.64%) or the global South (18.99%).
Taken together, the literature addresses a diversity of research questions which can be generally organised as relating either to the genesis or to the effects of gender quotas, with a few papers addressing both questions. The genesis of gender quotas has been much more studied in the case of electoral quotas than for other types of quotas. Reciprocally, research on board quotas focuses on their effects rather than on their genesis. Regarding the genesis of electoral quotas, the multiplication of casestudies has led to the identification of three main series of explanations, pertaining to the role of women's movements, the political environment and mechanisms of diffusion. Criteria used to evaluate the impact of electoral gender quotas usually follow the triptych of descriptive, substantive and symbolic representation. Studies generally identify positive effect in terms of increase in descriptive and substantive representation, yet draw more nuanced conclusions regarding symbolic representation. Research on the impact of board quotas looks into quotas' effects on the percentage of women on boards and on their characteristics (with generally positive results), as well as their impact on firm performance (with more mitigated results).
Altogether, research on gender quotas is very diverse. Nonetheless, it remains strongly segmented according to quota domain, research question, method and discipline. The two main research questions addressed in the gender quota literature, genesis and effects, largely corresponding to a partition between qualitative and quantitative methods. This echoes a broader feature of studies of policy adoption (with a dominance of qualitative methods) as opposed to studies of policy impact (dominated by quantitative approaches), beyond the case of gender equality. It is to be noted, however, that interest in gender quotas has led to the development of original methodological approaches which differ from this usual alignment, such as the use of history-modelling techniques to study gender quota adoption. The case of gender quotas could, in this perspective, function as a laboratory for methodological innovations in policy evaluation. More generally, research on quotas has been a breeding ground for methodological innovations in various directions, notably in comparative analysis and experimental methods, though these approaches so far remain quite separate.
Moreover, these two main research questions on the genesis and effects of quotas are most often treated separately. This is partly due to disciplinary focuses, as economics and management limit their approach to the question of impact while political science and sociology also tackle quota genesis. Research on quotas in economics and management on the one hand, and in political science and sociology on the other, would gain from further dialogue considering their different yet complementary approaches. Disciplinary frontiers thus tend to limit the possibility of more encompassing approaches. It is to be deplored, since a better understanding of the modalities and rationale of quota adoption and implementation could improve the quality and relevance of quota impact analysis. The genesis of electoral gender quotas is the object of abundant scholarly literature which evidences the importance of understanding the context for the enactment of a quota-from framing a policy problem, to finding a policy solution and implementing it-so as to address the question of its effects and to proceed to its evaluation. In efforts to evaluate such policies, scholars should be attentive to the political conditions in which they are adopted for they contribute to shaping policy design and, hence, outcome. Quotas' implementation modalities should be carefully considered to assess their effects with discernment.
The literature also remains very segmented according to quota domain: not only do few studies include both electoral and board quotas, but the two bodies of literature do not refer much to each other. In the case of quota genesis notably, this constitutes an important blindspot in academic production for, as evidenced by existing research, similar if not directly interrelated mechanisms oftentimes lead to their adoption. Cross-domain comparison is a propitious tool for scholars of public policy and gender equality. Firstly, through a shift in focus, it allows for a multiplication of viewpoints over similar policy problems; as such it contributes to curbing any narrow-sightedness resulting from the exclusivity of domain-specific research on gender quotas. Secondly, in terms of policy evaluation, the identification of crossdomain dynamics and mechanisms provides for a more holistic approach to the assessment of quotas as a gender equality policy, thus giving more accurate directions to policymakers and gender equality activists alike.
Finally, research on gender quotas has largely developed in isolation from research on quotas concerning other groups. To be sure, there has been something very specific to the diffusion and globalisation of quotas as a gender equality policy tool. However, gender is not the only domain where quotas have been put in place, and quota research would greatly benefit from further comparison with quotas for other groups.
While this scoping review has included the broadest possible array of research questions, methods and disciplines on gender quotas, there are still limits to its scope. For feasibility reasons, this review was limited to articles published in peerreviewed journals. The exclusion of edited books from the scope of the review represents a limit of this study, given the importance of book-based publications notably in political science (ex. Franceschet, Krook and Piscopo 2012;Lépinard and Rubio-Marin 2018;Engeli and Mazur 2022;Lang, Meier and Sauer 2023). Moreover, we have included only English-speaking and French-speaking references, to the detriment of other languages. The inclusion of references in Spanish, for example, would certainly lead to a more complete picture as all Latin American countries have legislated electoral quotas and Spanish-speaking scholars have been particularly prolific on the subject. Finally, given the timeframe between the initial search and the publication of the review, the present review is necessarily already outdated at the time of its publication. This, of course, is a difficulty all scoping reviews are faced with, but it is particularly salient for this body of research which has been characterised by an exponential growth.

Conclusion
The study of gender quotas not only represents a rich body of empirical literature, but it has also contributed to methodological innovations and important theoretical contributions. The 379 articles selected as part of this review reflect this diversity, as well as the exponential growth of this body of literature in the past few years. By taking into account the broadest possible array of disciplines and methods, we were able to shed light on the diversification of the literature in terms of disciplines, methods and quota domains under study (even though electoral and board quotas remain the two main domains of investigation). We have also identified gaps or imbalances in the literature, such as the lack of analysis of the genesis of corporate board quotas compared to the volume of research devoted to the genesis of electoral quotas. This diversity of approaches on an aggregate level, however, masks a persisting segmentation of the literature, in terms of disciplines involved, methods and research questions. This scoping review and the regrouping of references from different disciplines in a single database are a first step to favour a more systematic dialogue. Indeed, the synthetic format of the scoping review aims to facilitate researchers' familiarisation with inputs coming from other fields than their own. The complementary database provides easy access to the main references and research results from various disciplines on more specific topics or research questions that may be of interest to researchers. Based on our analysis of existing gaps in the literature, we highly encourage researchers to go beyond their initial research question when taking grounds in the existing literature: for example, impact assessment can be considerably improved, in terms of chosen criteria and the analysis of the mechanisms at play, by an understanding of the genesis of the quota in a given context, where it comes from and the way its goals were politically framed.
Expanding the scope of the literature review within a given quota project thus is the first step towards a more integrated and interdisciplinary evaluation. Eventually, research would greatly benefit from a more systematic integration of qualitative and quantitative methods, as well as different disciplinary perspectives, within the same project. This scoping review is a first attempt to open a dialogue between these different approaches and facilitate their cross-fertilisation.