Mapping issue salience divergence in Europe from 1945 to the present

Issue salience is a fundamental component of party competition, yet we know little about when, where, or why parties’ issue emphases converge or diverge. I propose an original operationalization of issue salience divergence, the extent to which parties’ issue emphases differ from each other in an election, that generates values at the party-election and country-election levels. I leverage data from party manifestos to calculate scores for 2,308 party-election combinations of 381 unique parties in 426 elections across thirty European countries, the most comprehensive dataset to date. I find that issue salience divergence is generally low and has starkly decreased over time, but countries and parties differ substantially. As an initial step in understanding these differences, I propose and test initial expectations of how party and democracy age, electoral systems, and party type alter the incentives for divergent issue salience.