Analyses of the Small Electoral Biases in Single-Member Constituencies

Abstract

Chapter 5 addresses the amplification of the first-past-the-post system’s operation of benefitting the largest party. In order to substantiate this inference, this chapter estimates electoral biases. An electoral bias is estimated by calculating the gap between the actual number and the notional number of seats for each of the parties concerned, assuming a uniform swing across all single-member constituencies. Therefore, the application of this framework to Japan suits the argument of this research. This chapter demonstrates that electoral biases are smaller in Japan than in the United Kingdom. Besides, this chapter demonstrates that they are often against the Liberal Democratic Party, although there are exceptions. This chapter also demonstrates that the geography component and the minor party victory component are large, although they vary, depending on the general election and the parties concerned. The small electoral biases suggest that the controversies surrounding the drawings of single-member constituencies such as malapportionment and gerrymandering matter little in Japan. This is in the sense that the homogeneous distributions of party supports prevent them from having a big impact on electoral results and not that malapportionment and gerrymandering have hardly happened.