The source of Japanese opposition to increasing defense commitments: The influence of electoral systems

The purpose of this study is to propose a theoretical explanation for the puzzle that Japan's defense commitment has remained low and inactive since the end of WWII, even though external strategic conditions and public preferences have shifted. Furthermore, through theoretical and empirical analyses, conducted with game theory and statistics, I will test my explanation as well.;Although there are many explanations for Japan's defense policymaking, they do not give us satisfactory answers to the puzzle, because they overlook the mechanism that directs the behavior of Dietmembers from the Liberal Democratic Party (LDP), who together have been most influential in forming defense policy. I argue that the electoral system--a single non-transferable voting (SNTV) system under a multi-member district (MMD)--nullifies the incentives for LDP Dietmembers to support defense expansion. LDP Dietmembers cannot easily support defense expansion under this electoral system, because doing so endangers their political status, whatever their personal preferences for defense expansion. More specifically, the legislators become indifferent to the national interest--including national security--because they have to devote themselves to providing pork-barrel programs to their personally loyal voters.;The theoretical comparison of SNTV under MMD with other electoral systems concludes that the electoral system is a sufficient condition but not a necessary condition to nullify the incentives of the legislators to expand defense. On the other hand, the empirical analysis discloses that the electoral system is a necessary condition as well. In other words, the legislators under SNTV with MMD necessarily cannot support defense expansion at the least. Since Representatives from the LDP chosen under this electoral system have final authority in the process of policymaking and a veto power over the Councillors, Japan cannot have increased defense commitments, even when necessity demands it. This is my answer to the puzzle of Japan's defense policy.