Mr. Abe was lauded for appointing five women to his cabinet in 2014; by late 2018, there was only one left. He is a cheerleader for “womenomics” and argues that the empowerment of women will boost the economy. Yet his ruling coalition is obstructing the advancement of women in politics — and that not only entrenches inequality; it also has economic costs.

The ratio of women among candidates in Sunday’s race was a mere 14.6 percent for Mr. Abe’s L.D.P. and 8.3 percent for its partner, Komeito. Among the four main opposition parties , however, the figure ranged from close to 36 percent (for the Democratic Party for the People) to more than 71 percent (for the Social Democratic Party). Those parties, combined with independent candidates supported by the opposition ( known collectively as “the unified opposition”), achieved near-parity with 49.6 percent of female candidates, far outperforming the ruling coalition, which averaged just over 13 percent.

Women now account for 17.5 percent of the L.D.P.’s members-elect to the upper house, compared with, say, more than 35 percent for members-elect from the Constitutional Democratic Party and 50 percent for the unified opposition.

Sunday’s was the first national election since the enactment of the Gender Parity Law, which promotes gender equality in politics and urges “making the numbers of male and female candidates as even as possible.” (I helped advise the nonpartisan parliamentary group that prepared the bill.) It took three years to enact, largely because of resistance from the L.D.P. The only reason the law eventually was passed by Parliament, known as the Diet, and unanimously, in 2018 is because it is nonbinding.

Still, the idea of gender parity has rapidly caught on among legislators. This spring, I headed a research team of six investigators that conducted a survey of Diet members in collaboration with the newspaper Mainichi. (We received 140 answers, a response rate of approximately 20 percent.) We asked respondents to say what they thought an appropriate ratio of women in the Diet would be. The mean of all their answers was 43 percent — much higher than the actual rates, namely 10 percent of the lower house and 20 percent of the (pre-election) upper house. Even among L.D.P. respondents, the answer was close to 38 percent.