‘‘Loyalty Norm’’: The Prevalence and Success of Coups

This article examines two competing theories that link variation in the size of a winning coalition to its members ’ incentives and ability to orchestrate coups d’état against authoritarian leaders. Selectorate theory’s ‘‘loyalty norm’ ’ focuses on the incumbent’s ability to buy support and the challenger’s inability to guarantee inclusion in a future coalition. It suggests that, in small-coalition systems, the probability of coup attempts and successesdecreases as coalition sizedecreases.Wedevelopanalternative theoryof polit-ical accountability that focuses on a coalition’s capacity to coordinate sanctions against a leader. It generates a rival expectation—in small-coalition systems, theprobability of coup attempts and successes increases as coalition size decreases.We evaluate these hypoth-eses through quantitative tests on coup attempts and successes during 1950 to 1999 and with an illustrative case study of the Saint-SylvestreCoup in the Central African Republic. These analyses provide strong support for our theory of political accountability