It may be sexist but when more women are on ballots, political parties do better, according to a new paper.

Whether or not that is because women will vote for gender over the best candidate is unclear, but it does mean that the belief that people will not vote for women is  not true. The authors analyzed changes on municipal election laws in Spain which instituted a quota for female candidates. With other factors being equal, the scholars found that 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 cast. 

"When you force a party to field more women, they gain votes," says Albert Saiz, the Daniel Rose Professor of Urban Economics and Real Estate in MIT's Department of Urban Studies and Planning, and director of MIT's Center for Real Estate, who is co-author of a forthcoming paper detailing the study. Democrats should take note. Republicans have more diversity but that may not be helping them. Focusing on getting more female candidates may instead be the road to true success.

Saiz believes that women do not appear on ballots as frequently as men because of machinations within party organizations. For local elections, Spain instituted a quota system mandating that 40 percent of candidates be women.

"We [believe] that it's not really about voters," Saiz says. "It's about internal dynamics of the parties. There's some elbowing out going on that leaves women behind."

The study makes adroit use of a natural experiment, a real-world circumstance that scholars in the "social sciences" can use to examine the causal impact of, say, a policy change within otherwise similar civic conditions. In this case, Spain's Social Democratic Party enacted an equality law after gaining power in the country's 2004 parliamentary election. The law requiring the 40 percent minimum quota of female candidates in local elections was put into effect for Spain's 2007 elections. 

If there were  a scarcity of qualified female candidates, it would have been manifest in the elections three years later - women would overwhelmingly lose. As a result of the legislation, the number of female candidates increased by 8.5 percentage points, or 32 percent, compared to 2004. Spain's law only applied to municipalities of more than 5,000 people; in some places, parties were already above the 40 percent threshold. So as a further refinement of the analysis, the researchers used towns unaffected by the quota as a control for the study. Saiz and Casas-Arce found that, given these controls, parties still produced the 4.2 percentage-point shift.

"If a party were optimizing, they couldn't do better if they fielded more females," Saiz says. "What we find is the opposite." 

While the findings are particular to Spain, the study itself was extensive: All told, the researchers examined elections in 4,852 municipalities. Among their additional findings: Voter turnout did not diminish in response to a greater number of female candidates.

"The effect is non-negligible, and it's positive," Saiz says.

Citation: Saiz et al.,"Women and Power: Unpopular, Unwilling, or Held Back?" upcoming in the Journal of Political Economy. It is co-authored by Pablo Casas-Arce, an assistant professor of economics at Arizona State University.