THE INCUMBENT ADVANTAGE IN JAPANESE LOWER HOUSE ELECTIONS: AN EMPIRICAL STUDY OF 1960-1990

摘要

This article shows how the incumbent advantage common in legislative elections worldwide has been tailored by Japanese political institutions - namely, the single non-transferable vote (SNTV) and institutionalised factionalism within the ruling Liberal Democratic Party (LDP) for the period 1960-1990. The author finds that, under the SNTV rule, the importance of incumbency in Japanese lower house elections varies both from a cross-sectional viewpoint and cross-temporarily. In regards to the cross-sectional aspect, incumbency is more important for candidates of LDP non-mainstream factions and candidates without LDP affiliation than those of the LDP mainstream factions in all major aspects of electoral achievement - total votes, voting percentage and winning a seat. After 1980, the margin of such a difference nevertheless shrank in terms of winning more votes, due to LDP factional reform in the late of 1970s. Such reductions, however, have not been significant enough to be reflected in terms of voting percentage and winning a seat.