Determining electoral districts in Japan: generations and living areas

Abstract

Currently, 289 of the 465 members of the House of Representatives are elected through a single-seat constituency system. These 289 seats are allocated to each prefecture according to population, with 7 seats in Ibaraki Prefecture, 12 seats in Hokkaido, and 30 seats in Tokyo for examples. Existing studies discussed how to determine the electoral districts with the main objective of correcting the vote-value disparity. In this paper, we focus on the disharmony between electoral districts and living areas, and the today’s silver democracy due to the declining birthrate and aging population, propose mathematical optimization models for dealing with them, and report numerical results based on real data.