A recent article by two prominent international relations theorists suggests that hypothesis-testing is “bad” for international relations (Mearsheimer and Walt 2013). These scholars suggest that “the creation and refinement of theory” is the most important pursuit international relations scholars ought to be engaged in. This book took an empirical puzzle about postwar Japan, namely, why the politicians who governed Japan for more than fifty years paid so little attention to national security before 1997 and so much attention after 1997, used theory from comparative politics to generate testable hypotheses that could explain this puzzle, and collected a wealth of new data to evaluate these hypotheses. It also used other theories to generate eight categories of alternative hypotheses and used other new data to evaluate these. Its conclusion, that the electoral strategies these politicians were forced to adopt under Japan's old electoral system made the costs of paying attention to national security prohibitive, and it was only when their electoral strategies changed after electoral reform in 1994 that the costs were lowered, contributes a new theoretical insight to the sub-field of international relations: that electoral systems influence security policy by influencing the costs of making security policy. This suggests that theory and careful hypothesis-testing need to go hand-in-hand, for it is only by elucidating and carefully testing hypotheses that new theories may be advanced.

The contributions of the book span the sub-fields of international relations and comparative politics, as well as the study of Japanese politics and Japanese security policy. For international relations, the book demonstrates that electoral systems influence security policy by influencing the amount of attention politicians can pay to it and the costs of changing it. Crucially, this influence is exercised independently of the level of concern politicians or their voters might have about national security and independently of any policy preferences or ideological inclinations they might hold. This confirms the findings of a growing body of work in international relations that establishes the impact of domestic political institutions on security policy (e.g. Bueno de Mesquita et al. 1999, 2003; Schultz 1999; Kaarbo and Beasley 2008; Davis 2008; Hymans 2011). It also demonstrates that democracies, like autocracies (Weeks 2008), vary in the extent to which people can hold leaders accountable for the provision of national security and other policies.

Chapter 1 described the puzzling turnaround in attention to national security by conservative Japanese politicians in 1997. Chapter 2 argued that this is best explained by a shift in their electoral strategies from pork for groups of voters in their respective districts to broad policy issues like national security, brought about by electoral reform to the House of Representatives (HOR) in 1994. Chapter 3 explained how candidate election manifestos and quantitative text analysis were used to obtain measures of the degree to which each of the 7,497 serious candidates competing in the eight HOR elections between 1986 and 2009 were relying on pork, policy, and within the policy category, national security policy. Chapters 4, 5, and 6 used those measures to test four hypotheses derived from the argument. Chapters 5 and 6 derived eight categories of alternative hypotheses that could plausibly account for both the shift in strategies and the turnaround in attention to national security, and tested those using measures of the ideological positions adopted by candidates during these eight elections, the topics of 126,275 voter petitions presented to the Diet during this time, public opinion polls, and other new data. Together, these chapters provide compelling evidence that conservative Japanese politicians began paying more attention to national security in 1997 because their electoral strategies changed, and not because of any other variable.

This begs the question, what influence has their new attention to national security had on Japanese security policy? Before answering this question, it is important to think about why it is difficult to evaluate the relationship between their new electoral strategies and Japanese security policy. This is because we cannot observe what Japanese security policy would have looked like in the absence of their new electoral strategies. The standard approach for scholars interested in evaluating the causal impact of a treatment like electoral reform on an outcome like security policy is to identify a set of countries that resemble Japan, some of which received the treatment and some of which did not, and examine what their security policies look like after some received the treatment. If the security policies across the two sets of countries were then found to vary, we could attribute that variation to the effects of the treatment because we know the countries were similar in other regards before they received the treatment.

Chapter 1 described the puzzling turnaround in attention to national security among conservative Japanese politicians in 1997. This chapter argues that the best explanation for this turnaround is a shift in their electoral strategies, brought about by electoral reform to the House of Representatives (HOR) in 1994. The first election under the new system was held in October 1996, just three months before these conservative politicians plucked the abduction and other security issues from relative obscurity to champion in the Diet and elsewhere. The explanation presented draws upon studies of Japan's electoral reform, which find that it altered politicians’ relationships with voters, supporters, interest groups, central government bureaucrats, and the party leadership (e.g. Christensen 1998; Cox, Rosenbluth, and Thies 1999; Horiuchi and Saito 2003; Krauss and Pekkanen 2004; Carlson 2006; Hirano 2006; Krauss, Pekkanen, and Nyblade 2006; Krauss and Naoi 2009; Horiuchi and Saito 2010), and studies of the policy impacts of electoral systems, which find that certain policies are more or less likely when a country adopts or is adopting a particular electoral system (e.g. Bernhard and Leblang 1999; Persson and Tabellini 2000; Lizzeri and Persico 2001; Rosenbluth and Thies 2001; Milesi-Ferretti, Perotti, and Rostagno 2002; Rogowski and Kayser 2002; Golden 2003; Rosenbluth and Schaap 2003; Iversen and Soskice 2006; Chang 2008; Estevez-Abe 2008; Rosenbluth and Thies 2010; Rickard 2010, 2012a,b; Weinberg 2012). In both of these literatures, the mechanism through which electoral systems are thought to have their effects is electoral strategy: politicians are thought to adopt different electoral strategies under different electoral systems, and it is their adoption of these different strategies that encourages them to form different relationships with other political actors and choose different policy outcomes.

The chapter proceeds as follows. First, it uses two rules, the electoral system and constitutional structure, to explain why the electoral strategies adopted by conservative Japanese politicians prior to electoral reform would have made it extraordinarily difficult for them to pay attention to broad policy issues such as national security.