Political parties and lawmakers should not sit idle in the wake of inconclusive high court rulings recently on whether the gap in vote value between electoral districts in the Lower House election in December violated the principle of equality under the Constitution. Although the courts delivered mixed decisions, the parties need to come to grips with the grave nature of the issue at stake — whether the popular will of voters is accurately represented in the Diet — and take swift action to correct the imbalances.

Right after Prime Minister Shinzo Abe's ruling coalition swept to a two-thirds majority in the Lower House in December's snap election, two groups of lawyers filed 17 lawsuits with high courts and their local branches seeking to invalidate the outcome of races fought in the chamber's 295 constituencies across Japan. In the election, the maximum gap in the value of votes between populous and less populous constituencies reached 2.13 to 1. Ballots cast by voters in the Miyagi No. 5 constituency had 2.13 times more weight in electing Lower House members than votes cast by people in Tokyo's No. 1 electoral district.

So far, rulings have been handed down in 14 of the 17 suits, with widely varying court decisions. The Fukuoka High Court, in its Wednesday decision, ruled that the elections in the constituencies of Fukuoka, Saga, Nagasaki, Oita and Kumamoto prefectures were "unconstitutional" but did not go as far as to invalidate the results. Vote-value disparity was judged to be "in a state of unconstitutionality" in nine other court decisions, while four courts ruled that the December election was "constitutional," noting that the gap in vote value was not as wide as to infringe on equality under the Constitution.

After three more high court suits are decided by late April, all the cases will be sent up to the Supreme Court, which is expected to hand down its decisions either late this year or in early 2016.

The gap in the value of votes between electoral districts has been a serious problem in national elections for decades. The legitimacy of national elections has been challenged each time a Lower House or Upper House race was held.

The Supreme Court has ruled that the maximum 4.99-to-1 disparity in vote value during the 1972 Lower House election and the 4.40-to-1 gap in the 1983 race as "unconstitutional" — though the election results were allowed to stand.

The top court determined that the gap in the value of votes in the first three Lower House elections held after the current system of combining single-seat constituencies and proportional representation was introduced in 1994 was allowable.

But the elections in 2009 and 2012 — in which the maximum vote-value gap was 2.30 to 1 and 2.43 to 1, respectively — were judged to be "in a state of unconstitutionality."

In the 2011 ruling on the 2009 election, the Supreme Court specifically called for abolishing a system that grants one seat to each of the nation's 47 prefectures then distributes the remaining seats according to their population. While the system had been introduced to ensure a certain level of representation for depopulated areas in national politics, the court said it stands in the way of correcting the gap in the value of votes. This system was effectively retained when the Diet amended the election law in 2013 for a partial reapportionment of seats between constituencies.

This partial reapportionment temporarily brought down the maximum vote-value disparity ratio to within 2 to 1, but it widened to 2.13 to 1 by the December 2014 election due to the continuing population flight from rural to urban areas.

In handing down the sole "unconstitutional" ruling among the 14 court decisions so far, the Fukuoka High Court pointed out that the structural deficiency in the system of allocating one seat to each prefecture has not yet been resolved, resulting in a situation that "runs counter to the demand for equality in vote value." The court said the problem has not been resolved "within a reasonable period of time" since it was first pointed out in the 2011 Supreme Court ruling.

Although the Fukuoka court turned down the plaintiffs' demand for invalidating the election results, it does not mean it condoned the status quo. It pressed the Diet to find a fundamental solution to the problem. Other high courts that gave more lenient "state of unconstitutionality" decisions also highlighted the insufficient efforts by the legislature to correct the disparity in the value of votes.

Members of the Diet must not think that they were let off the hook just because the election results have not been invalidated. They should not wait until the Supreme Court hands down a final verdict on the December election but instead act quickly themselves to resolve the problem. Narrowing the disparity to just within 2 to 1 is not a solution. It still means that people in some constituencies have nearly twice the power to elect representatives to the Diet as their counterparts in other districts — a gross distortion of popular will.

Lawmakers and parties involved in Lower House electoral reforms have been unable to come to an agreement themselves and have left the matter to discussions by a third-party panel of experts under the chamber's speaker. The panel is now weighing a new system that allocates seats among prefectures more accurately along the population breakdown than the current one. If the current number of 295 single-seat constituencies is to be maintained, the system would cut one seat each from nine prefectures and add a total of nine seats to six prefectures. The parties involved should accelerate the talks and agree on specific reforms as quickly as possible.

Efforts to correct the disparity in the value of votes in Upper House elections — which is even wider than in the Lower House — also remain slow. Talks among the parties involved have been delayed by the Liberal Democratic Party's failure to forge a consensus among its own members.

Time is short if the chamber's electoral reforms are to be implemented in time for the next triennial election in the summer of 2016. Members of both Diet chambers need to act fast on this longtime problem that affects people's rights to equality in voting.