The recent Takamatsu High Court decision that the gap in the value of votes in the Upper House election in July was “in a state of unconstitutionality” challenges the Diet to fulfill its overdue promise to fundamentally overhaul the chamber’s electoral system. While this was only the first in a series of rulings expected on more than a dozen lawsuits filed across the country over the last election, the Takamatsu court’s decision that the maximum disparity of 3 to 1 in vote values was “impermissible under common sense” must be taken seriously.

Disparities in the value of votes between electoral districts emerge due to differences in the number of eligible voters per Diet seat allocated to districts. A ballot cast by a voter in a less-populous constituency carries more weight in electing a lawmaker than a vote in a more populous district if the same number of seats are allocated to both constituencies. The disparity is a grave issue that deviates from equality under the law and threatens to distort the representation of popular will in the Diet.

The Takamatsu court ruled that the disparity in the latest Upper House election was unacceptable given that the gap was within 2 to 1 in the last Lower House election in 2017. There are no justifiable excuses for lawmakers to further delay an overhaul of the Upper House electoral system to fundamentally address the problem.

Earlier, courts were more lenient toward the sharp disparity in the value of votes in Upper House elections. The Supreme Court ruled that the gap in the 1992 election — which widened to as much as 6.59 to 1 — was in a state of unconstitutionality but fell short of invalidating the race as unconstitutional. As seats were then reallocated across constituencies to reduce the disparity, a maximum disparity of around 5 to 1 was long deemed acceptable until the top court ruled the 5 to 1 gap in the 2010 election and the 4.77 to 1 disparity in the 2013 race to be in a state of unconstitutionality. The Supreme Court called for an overhaul of the electoral districts based on prefectural borders.

A 2015 amendment to the law on the election of public offices combined several less-populous prefectures into two constituencies: one encompassing Tottori and Shimane and the other pairing Tokushima with Kochi. Subsequently, the maximum vote value gap in the 2016 election narrowed to 3.08 to 1. The Supreme Court ruled the disparity was constitutional, but that was only because a legal provision attached to the 2015 amendment promised that the Diet would carry out a fundamental overhaul of the electoral system by the next election in 2019.

However, that promise was never fulfilled as political parties in the Diet failed to reach a consensus in time for the 2019 election. The ruling Liberal Democratic Party pushed a partial reform through the Diet that was meant to narrow the maximum vote value gap barely within 3 to 1 but increased the number of Upper House seats by six. But as long as the population exodus from rural to urban areas continues, it’s certain the disparity will keep expanding. The Takamatsu court ruling dismissed the partial reform as nothing more than a stopgap measure.

Efforts to redistribute Diet seats according to the population dispersal often encounter criticism that voters in depopulated areas lose representation in national politics. The creation of electoral districts combining two prefectures has caused voter apathy in prefectures that do not have hometown candidates running in the election. Voter turnout in the July election was the lowest in Tokushima Prefecture at a mere 38.59 percent, while turnout was at a record low in the Tottori-Shimane constituency.

The LDP has compiled a draft amendment to the Constitution mandating that at least one lawmaker be elected from each of the 47 prefectures in each triennial Upper House election. However, the Takamatsu court ruling noted that the prefecture-based constituency system should be overhauled if that stands in the way of fundamental reform of the electoral system. It said that if the creation of electoral districts combining two prefectures is causing so many problems, those problems should be addressed by exploring an electoral system not based on prefectural borders.

There have been proposals made about such electoral systems, including dividing the nation into nine proportional representation blocs, or creating 11 large constituencies that elect multiple lawmakers. The issues of whether similar electoral systems should be maintained for both the upper and lower chambers of the Diet — combining constituency races and proportional representation votes — and the roles each of the two chambers should play will need to be on the agenda of discussions for electoral reforms. All political parties should work together to explore ways to narrow the disparity in the value of votes within a permissible range.

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