Measuring Voters’ Multidimensional Policy Preferences with Conjoint Analysis: Application to Japan’s 2014 Election

Representative democracy entails the aggregation of multiple policy issues by parties into competing bundles of policies, or manifestos, which are then evaluated holistically by voters in elections. This aggregation process obscures the multidimensional policy preferences underlying a voter's single choice of party or candidate. We address this problem through a conjoint experiment based on the actual party manifestos in Japan's 2014 House of Representatives election. By juxtaposing sets of issue positions as hypothetical manifestos and asking respondents to choose one, our study identifies the effects of specific positions on the overall assessment of manifestos, heterogeneity in preferences among subgroups of respondents, and the popularity ranking of manifestos. Our analysis uncovers important discrepancies between voter preferences and the portrayal of the election results by politicians and the media as providing a policy mandate to the Liberal Democratic Party, underscoring the potential danger of inferring public opinion from election outcomes alone.