Why are There More Women in the Upper House?

In directly elected bicameral legislatures without a quota system, there is often a large disparity in the percentage of women's representation between the two chambers. Japan is no exception to this rule. The share of women members in the upper house (23.1%) is twice as high as that in the lower house (9.7%). Furthermore, the former has consistently outnumbered the latter for decades. The disparity between the two chambers may be the results of differences in electoral systems, but that cannot fully explain it. We explore the mechanisms behind this disparity through two survey experiments from the perspectives of both voters (demand side) and candidates (supply side). Our findings show that voters become more supportive of women candidates in upper house elections when they are informed that the upper house plays a subordinate role in decision-making. Moreover, women are found to be more willing to run for office when they are informed about the job security that accompanies an upper house position, whereas men are less willing to run when they are informed about the limited power of the upper house to appoint the prime minister. These results suggest that the institutional priming conditions people's attitudes toward women candidates and their willingness to run for office, resulting in a large disparity in the percentage of women representatives between the two chambers in the bicameral legislature.