Ticket-splitting in mixed-member systems: on the importance of seat linkage between electoral tiers

In mixed-member electoral systems, voters usually have two votes: a nominal and a list vote. According to some studies, voters are increasingly using them to cast a split-ticket vote. However, very little is known about whether the type of mixed-member system, and in particular whether the allocation of seats across tiers is linked or not, creates different sets of incentives for this behaviour. This article provides new insights into the topic by analysing survey data from seven countries and 18 elections since 1990. It is found that the proportion of split-ticket votes is greater in mixed-member proportional than in mixed-member majoritarian systems. The results suggest that voters understand the operation of the electoral system and its consequences for the distribution of seats among parties, and adapt their behaviour accordingly.