The past two decades have seen a global explosion in the adoption and implementation of gender quotas. In many countries, these gender quota laws and intraparty rules have dramatically altered the presence of women in public office, in some cases taking legislative bodies, where women were present in only trivial numbers, and transforming them almost instantaneously into parliaments, where women occupied between a quarter and a third of the seats. Prime examples of this dramatic transformation include the Costa Rican Legislative Assembly where women accounted for a mere 14% of the deputies as late as 1998 and by 2002 held 35% of the seats, the Argentine Senate where in 2000 women occupied only 3% of the seats but in 2001 comprised 33% of the Senate, and the Honduran Congress where the percentage of female deputies jumped from 6% in 2005 to 23% in 2006.

The current scholarly literature provides us with a relatively solid understanding of how gender quota laws and intraparty rules interact with other institutional factors, as well as (albeit to a lesser extent) of the broader political context to affect the proportion of legislators elected who are women. Much less well understood are two crucial aspects of quotas for women: their origin and their impact on substantive representation. This outstanding book expertly addresses the former gap in the literature, representing a profound advance in our understanding of the adoption and implementation of gender quotas throughout the globe.

Mona Lena Krook explores the adoption and implementation of three distinct types of gender quotas: legislative quotas, party quotas, and reserved seats. With legislative quotas, there is either a statutory or constitutional requirement that a minimum percentage of women (or maximum percentage of candidates from either sex) appear as candidates in legislative elections. This quota legislation applies across all parties, and, normally, across all electoral districts. Party quotas are rules adopted internally by individual political parties that specify a minimum percentage of candidates who must be women (or a maximum for either sex) in a legislative election in either an electoral district or overall. Reserved-seat systems, as the name implies, set aside a specific percentage of legislative seats exclusively for women. While one finds a mixture of the three types of quotas globally (particularly in regard to legislative and party quotas), legislative quotas have tended to be most common in Latin America, party quotas are most frequently found in Europe and sub-Saharan Africa, and reserved seats predominate in the Middle East and North Africa.

After a concise introduction (Chapter 1), the book begins with an impressive review and analysis of the extant literature on gender quota adoption and implementation (Chapters 2 and 3). Given that a majority of this literature has focused either on single countries or regions (in particular, Africa, Europe, and Latin America), Krook provides a tremendous service to the discipline by bringing together this vast corpus of work in a comprehensive summary of the existing principal explanations for the adoption and subsequent successful or unsuccessful implementation of gender quotas in the world.

Krook next evaluates the predominant explanations for quota adoption and successful/unsuccessful implementation via three detailed, paired country comparisons. These six countries represent examples of the employment of one of the three types of quotas (legislative, party, reserved seat), as well as cases where multiple quota reform efforts have been attempted. Within the pairs, one case represents a gender quota success, where the adoption and implementation of quotas resulted in noteworthy increases in the presence of women in the national legislature, while the other case represents a gender quota failure, where the adoption and implementation of quotas failed to have a significant effect on the election of women legislators to the parliament.

Chapter 4 studies two cases (India and Pakistan) where reserved seats were adopted. Pakistan's use of reserved seats for the national legislature is the success, while India's inability to extend reserved seats utilized at the municipal level to national parliamentary elections is the failure. Chapter 5 examines two cases (Sweden and the United Kingdom) where party quotas have been utilized, with great success in Sweden and with very limited success in the United Kingdom. Chapter 6 analyzes two cases (Argentina and France) where legislative quotas have been employed, with Argentina's successful law resulting in an almost tenfold average increase in the percentage of women in the national bicameral legislature and the French law's impact, conversely, having been extremely modest.

Krook concludes with six principal lessons based on the analysis of these six country cases. First, there is no one way to achieve the adoption of gender quotas, which in these countries arrived via very different pathways. Second, international actors (e.g., the United Nations Division for the Advancement of Women, the Inter-American Development Bank's PROLEAD) and global and regional networks of women have played a prominent role in the adoption of quotas throughout the world, though this has not been fully appreciated in the scholarly literature. Third, normative considerations exercise a profound impact on the debates over the adoption and implementation of quotas, but, fourth, political strategic calculations also play a powerful role in the quota debate process.

Fifth, the actual impact of quotas on the election of women legislators is heavily conditioned by the interaction between the quota legislation/rules and the institutional and political context of the country, party, and/or locality. Related is the sixth and final lesson, which underscores that not all quotas will have the same impact, and that quota designers must take into account other relevant features of an electoral and party system as well as key aspects of party and political culture. This suggests that while there are several general rules that can guide us in the adoption of gender quotas (e.g., all things being equal, quotas implemented in concert with closed-list electoral systems with placement mandates are moderately superior to those with open-list systems, which lack placement mandates), potential reformers are well advised to take seriously the institutional, political, and cultural context in which the gender quotas will be employed.

Krook has written a truly outstanding book that is destined to become a mandatory reference in the thematic area of gender and representation. She combines exceptional theory with outstanding analysis of six critical cases to provide the most comprehensive global study of gender quota adoption and implementation to date. The book is a must-read for all scholars concerned with the role of gender in politics. Institutionalist scholars will also find it of great interest as a result of the author's illuminating study of the electoral reform process. Finally, students of representation more generally will benefit from Krook's comparative insights on the varying success of positive-action reform efforts across space and time.