The Supreme Court ruling last week that the October 2017 Lower House election — in which the maximum disparity in the value of votes between electoral districts was 1.98 to 1 — was constitutional does not put an end to the problem in which a ballot in a less populous constituency carries as much as around twice the weight as one in a more populous district. Officials and lawmakers need to be reminded of the gravity of the problem — which distorts the representation of popular will in the Diet — and maintain constant efforts toward eliminating the disparity, which runs counter to the equality principle under the Constitution.

The decision by the top court — which had earlier ruled that the previous three Lower House elections in 2009, 2012 and 2014 were all in a "state of unconstitutionality," while falling short of invalidating the vote results as unconstitutional — apparently reflects the improvements made to the disparity in the election last year. A 2016 amendment to the Public Offices Election Law, made in response to the repudiation of the vote value gap in the earlier elections, cut six seats from the Lower House and redrew the borders of 97 electoral districts to keep the maximum disparity within 2 to 1 for the first time since the current electoral system combining single-seat constituencies and proportional representation blocs was introduced in 1996. The maximum gap in the value of votes reached 2.3 to 1 in the 2009 election, 2.43 to 1 in 2012 and 2.13 to 1 in 2014.

The 2016 revision also calls for the introduction of a new system of distributing Lower House seats across constituencies that better represents the population dispersal among the nation's 47 prefectures — although implementation of that system was delayed until it reflects the outcome of the 2020 national census. The new system is expected to keep the maximum disparity in vote value within 2 to 1, and the Supreme Court ruling, which dismissed the lawsuit filed by a group of lawyers demanding that the 2016 Lower House election be invalidated, noted that legislative steps have been taken to significantly narrow and stabilize the disparity.