This book studies the proportion of women in national parliaments. More precisely, it seeks to identify the factors that influence the percentage of female parliamentarians, paying particular attention to the electoral system. The author seeks to understand a profound political movement, that of the third wave of democratization of political systems, through the particular perspective of female representation in parliaments. Although several books have been published on women in politics, none have focused on electoral systems as an explanation for the proportion of women in national parliaments.