Is the single nontransferable vote superproportional? Evidence from Japan and Taiwan

Theory: The traditional view of the single nontransferable vote (SNTV) system has been that it is superproportional-tending to produce larger seat bonuses for small parties than for large parties-because small parties face easier nomination and vote division problems than do large parties. A contrary view is that SNTV privileges governing parties by giving them superior access to particularistic policy benefits, which are useful in stabilizing both nominations and vote divisions within parties. Hypotheses: By the latter view, SNTV should lead to subproportional results-with larger seat bonuses for large parties than for small parties-to the extent that governing parties are large. Methods: In this paper, I operationalize and test these competing claims at the district level, using both cross-tabulations and probit analysis. Results Although there is a sense in which SNTV is superproportional, I show that two large governing parties (the LDP of Japan and the KMT of Taiwan) have been significantly more efficient at securing as many seats as possible out of a given maximum number of winnable seats, than have their respective oppositions.