The percentage for the U.S. Senate is slightly higher, however, with women making up 25 percent.
Rwanda ranked No. 1, with 61.3 percent of its lower house made up of women. Tied for last place were the Federated States of Micronesia, Papua New Guinea and Vanuatu, which have no women in their parliaments.
With women holding 1 in 10 seats in its lower house, Japan ranked lowest among the Group of 20 industrialized nations. Mexico, which came in fourth, with women making up 53.1 percent of its lower house, ranked highest among G-20 members.
In the top 25 were the Nordic nations of Denmark, Finland, Iceland, Norway and Sweden, often hailed for their gender-equality policies. They placed 25th, 12th, 21st, 14th and fifth, respectively.
Chile, where a local government official made news this week by saying that women are fully free and content with poems and roses, placed 88th.
Some leadership experts have suggested that 30 percent is the point at which women are able to hit a “critical mass” to influence politics or hold sway in male-dominated industries. Others, however, argue that number may still be too low to truly reshape cultural attitudes or political discourse — or even to shift perceptions about women in politics in general.
If 30 percent were to be used as a benchmark, then only 50 of the 193 countries in the study would have made the cut.