Vote-value Disparities in Lower House Election: Use ‘Constitutional’ Ruling as Opportunity to Advance System Reform

Editorial

15:12 JST, September 27, 2025

Even though the judiciary has handed down a ruling of constitutionality, it does not mean that the problem of the House of Representatives election system has been resolved.

Merely working to correct vote-value disparities will only lead to a decline in the number of lawmakers elected from constituencies in regional areas, making it harder for the voices of those living in less populated areas to reach national politics. It is time for ruling and opposition parties to seriously work on election system reform.

Regarding the lower house election in October 2024, in which the maximum vote-value disparity was 2.06-to-1, the Second Petty Bench of the Supreme Court ruled it constitutional. It stated, “There is rationality in the current election system, and it cannot be said that it has reached the point at which equality was violated in terms of the value of a vote.”

Based on judicial rulings demanding that vote-value disparities be corrected, last year’s lower house election was the first held using the so-called Adams method, under which the seats allocated to each prefecture in the Diet are adjusted to be more in proportion with the population. The “plus 10, minus 10” plan was carried out, in which a total of 10 seats were added for urban areas, while 10 seats were subtracted from regional areas.

Going forward, the zoning of constituencies is supposed to be reviewed when the disparity exceeds 2-to-1 in the census conducted every five years. This is a system in which disparities are corrected periodically. It is quite natural that the Supreme Court evaluated the Diet’s reform efforts, including the introduction of the Adams method.

This lawsuit was filed at 14 high courts and their branches nationwide. All high court rulings upheld the constitutionality of the disparity of the lower house election.

Each time a national election has been held, lawsuits have been filed one after another on the grounds of minor disparities, and as a result, the Diet has been swayed by these lawsuits. Some may find this situation strange.

If zoning is frequently reviewed in response to population shifts, voters could become confused. As long as more people continue to move to Tokyo, the number of constituencies in regional areas will only decrease.

The problem is not limited to vote-value disparities. Last year, ruling and opposition parties established a council on election system reform in the lower house, and discussions have been progressing. However, they have yet to produce concrete reform proposals.

If they fail to reach a conclusion as a result of trying to include strategic considerations to benefit their parties, one option is to establish an election system council comprising experts and others in the government to examine the issue.

Even more problematic than the lower house election system is that of the House of Councillors. To correct vote-value disparities, merged constituencies were introduced in 2016. Constituencies were integrated by combining neighboring prefectures and voter interest in candidates from the other prefecture is low, resulting in continued low voter turnout. If this continues, representative democracy could be shaken.

The Constitution defines members of both houses of the Diet as “representatives of all the people.” It would be worthy of consideration to revise this expression and position upper house lawmakers as regional representatives, so as to reflect regional voices in national politics.

Both houses need to collaborate and deepen discussions, including reviewing their respective roles.

(From The Yomiuri Shimbun, Sept. 27, 2025)