National Diet - Composition

Composition

See also: Elections in Japan and List of members of the Diet of Japan

The houses of the diet are elected under a parallel voting system. This means that the seats to be filled in any given election are divided into two groups, each elected by a different method; the main difference between the houses is in the sizes of the two groups and how they are elected. Voters are also asked to cast two votes: one for an individual candidate in a constituency, and one for a party list. Any national of Japan at least twenty years of age (the age of majority in Japan) may vote in these elections. Japan's parallel voting system is not to be confused with the Additional Member System used in many other nations.

• House of Representatives: Of 480 members, 300 are elected from single seat constituencies under the Single Member Plurality ("First-past-the-post") system, and 180 are elected from eleven separate electoral blocs under the party list system of proportional representation (PR).
• House of Councillors: Of 242 members, 146 are elected from 47 prefectural constituencies by means of the Single Non-Transferable Vote. The remaining 96 are elected by open list PR from a single national list.

The Constitution of Japan does not specify the number of members of each house of the Diet, the voting system, or the necessary qualifications of those who may vote or be returned in parliamentary elections, thus allowing all of these things to be determined by law. However it does guarantee universal adult suffrage and a secret ballot. It also insists that the electoral law must not discriminate in terms of "race, creed, sex, social status, family origin, education, property or income".

Generally, the election of Diet members is controlled by statutes passed by the Diet. Because the Liberal Democratic Party has controlled Japan for most of its postwar history, and gains much of its support from rural areas, rural areas generally have more representation in the Diet than do urban areas. The Supreme Court of Japan began exercising judicial review of apportionment laws following the Kurokawa decision of 1976, invalidating an election in which one district in Hyōgo Prefecture received five times the representation of another district in Osaka Prefecture. The Supreme Court has since indicated that the highest electoral imbalance permissible under Japanese law is 3:1, and that any greater imbalance between any two districts is a violation of Article 14 of the Constitution. In recent elections the malapportionement ratio amounted to 4.8 in the House of Councillors (census 2005: Ōsaka/Tottori; election 2007: Kanagawa/Tottori) and 2.3 in the House of Representatives (election 2009: Chiba 4/Kōchi 3).

Candidates for the lower house must be 25 years old or older and 30 years or older for the upper house. All candidates must be Japanese nationals. Under Article 49 of Japan's constitution, Diet members are paid about ¥1.3 million a month in salary. Each lawmaker is entitled to employ three secretaries with taxpayer funds, free train tickets, and four round-trip airplane tickets a month to enable them to travel back and forth to their home districts.