Why some electoral systems are perfectly stable, and others are not?

This article addresses a recurrent yet unanswered question in electoral studies: why in some countries have never changed their electoral system, while others have continuously reformed it. The existing literature has given several explanations of why particular electoral arrangements were chosen at particular point in time. These explanations usually highlight the importance of the strategic behaviour of key political actors. However, they fail to give a convincing explanation for why some electoral systems are perfectly stable throughout time. In this article, we investigate under which conditions key political actors start considering a potential change of electoral system. We argue that a change in the electoral rules is more likely when there is a mismatch between the actual party system and the expected party system the electoral system should produce. In other words, this is when there is a disequilibrium between the two, that political actors start considering electoral reforms.