When political parties field more women, they score more votes

With other factors being equal, the research found, parties that increased their share of female candidates by 10 percentage points more than their opponents enjoyed a 4.2 percentage-point gain at the ballot box, or an outright switch of about 20 votes per 1,000 casts.

Co-author Albert Saiz said that when you force a party to field more women, they gain votes and believes the study strikes a blow against some common justifications for the dearth of female candidates in many democracies, namely, that voters simply prefer voting for men, or that not enough high-quality female candidates are available to political parties.

It is likely that voters will support women, he thinks, and that plenty of good female candidates exist, but women do not appear on ballots as frequently as men because of machinations within party organizations.

Saiz added that they believe that it's not really about voters, it's about internal dynamics of the parties. There's some elbowing out going on that leaves women behind.

These results are not consistent with the existence of major voter aversion to female candidates, the authors write in the paper. Saiz says he would welcome further research on the subject, including studies of mechanisms that might make it easier for women to become candidates, such as the greater use of party primaries at all levels of politics.

At a minimum, he notes, the study gives parties with a prior lack of female candidates an obvious incentive to remedy that, adding that the effect is non-negligible and it's positive.

The study will appear in the Journal of Political Economy.