Cross-country comparison of the Incumbency Advantage: the need for bounds and evidence from 38 countries

The systematic comparison of the incumbency advantage across multiple countries' legislatures has proven elusive, in part because the incumbency advantage is defined and estimated differently across settings. To achieve comparable estimates, we focus on the individual advantage, not the party's, and use a regression discontinuity design comparing winners and runners-up. We define the incumbent-runner-up advantage and construct bounds for it. We then show that the upper bound of this object coincides with the upper bound of the incumbent-challenger advantage, the empirical counterpart of the theoretical definition of the incumbency advantage. The resulting 'upper-bound incumbency advantage' can be estimated in any electoral setting and is meaningful across both concepts. With data for 38 national legislatures, we provide the first like-for-like cross-country comparison of the incumbency advantage and relate it to electoral turnover, economic development, democratic quality, corruption, and electoral systems.