Voters’ Left–Right Perception of Parties in Contemporary Japan: Removing the Noise of Misunderstanding

The prevailing theory states that either Japanese voters have stopped ideologically distinguishing parties or that the main political parties in Japan have become more centrist in recent years. These arguments are based on survey questions asking citizens to locate parties on an ideological scale. However, these questions may suffer from noise caused by respondents who misinterpret the question wording or answer the questions inappropriately to mask their misunderstanding of the terms ‘left’ and ‘right’. To address this problem by extracting only the views of those who know the meaning of left–right terms, this article develops a mixture model. Applying the model to an opinion poll conducted after the 2012 Japanese general election, I confirm that those who comprehend the left–right terminology – slightly over half of all voters – largely perceived parties’ ideologies in the same way as experts. Additionally, I find that even these voters face difficulties in placing ambiguous or new parties on the political spectrum. This study has implications not only for understanding trends in Japanese political ideology, but also for survey design and analysis of heterogeneous survey responses.