The Liberal Democratic Party's draft plan to amend the Constitution to eliminate Upper House electoral districts that combine more than one prefecture addresses only one aspect of the complicated problems afflicting the electoral system. The LDP's plan seeks to make sure that at least one Upper House member is elected from each of the nation's 47 prefectures when half of the seats in the upper chamber come up for grabs every three years. It is a response to the creation of two pairs of constituencies that combined less populous prefectures, Tottori with Shimane and Tokushima with Kochi, in the 2016 election as part of the efforts to narrow the large disparity in the value of votes between electoral districts.
LDP lawmakers argue that depopulated areas of the country will lose representation in national politics if Diet seats are allocated strictly according to population dispersal. That problem will indeed get more serious as population flight from rural parts of Japan to large urban areas continues unabated. In 2017, 40 of the 47 prefectures suffered a net population outflow, while the net inflow to the greater Tokyo area (also comprising Saitama, Chiba and Kanagawa) accelerated to nearly 120,000 people.
But merely stipulating in the Constitution that at least one Upper House member be elected from each prefecture ignores the problem of the gap in vote values across constituencies, which runs counter to the principle of equality under the law as guaranteed in Article 14. Characterizing Upper House members as representatives of the prefectures that elect them also raises the question of consistency with Article 43, which stipulates that both houses of the Diet "shall consist of elected members, representatives of all the people."