The Intensity of Government–Opposition Divide as Measured through Legislative Speeches and What We Can Learn from It: Analyses of Japanese Parliamentary Debates, 1953–2013

Through the analysis of legislative speeches made by prime ministers and party representatives in parliamentary sessions in Japan from 1953 to 2013, we argue that it is possible to place parties according to a dimension that captures their confrontational nature within a parliamentary democracy and its evolution over time. Using this dimension extracted via a well-known scaling algorithm (Wordfish), we develop an index of the intensity of the government–opposition divide that is directly related to the dynamics of the electoral cycle of Japanese politics. We then show how this new index greatly facilitates the investigation of two important aspects of Japanese legislative politics (the survival rate of governments and the speed of passage of cabinet bills) compared to a situation in which we focus on more traditional measures capturing the ideological position of the parties alone.