Download our paper prepared for the APSA 2022 Annual Meeting that proposes a new typology of parliamentary party switches.
Abstract. We propose a new typology of parliamentary party switches (switching events) that focuses on three dimensions: (1) the number of MPs and the degree of coordination, (2) the origin of switchers and (3) the destination of switchers – a parliamentary party group (PPG) or independent status. We further distinguish between switches with single and multiple destinations. Our approach sheds new light to party instability in various ways. We elucidate types of party instability to emphasize the complexity of party instability that have eluded the conceptual toolset available thus far. For example, “collective defection” (coordinated movement from one PPG to another), “collective exit” (MPs exiting their parliamentary group to become independent MPs) and “multi-PPG split” (coordinated moves from several PPGs to form a new PPG). Using preliminary data compiled for Instaparty (Party Instability in Parliaments) project from (mostly) Poland and Ireland, we find rich diversity in the forms of parliamentary party instability. While individual defections are much more common than group defections, they are clearly more dominant in Ireland than in Poland; furthermore, switches between PPGs (rather than between PPGs and independent status) have been more common in Poland. Our typology is illustrated by the analysis of the 8th Polish Sejm that provides examples of nearly all single-origin switching events and of most multi-origin ones. The new typology presents the first step of our inquiry into the patterns, causes and consequences of party switching in eight democracies (Estonia, Ireland, Italy, Lithuania, Norway, the Netherlands, Poland and Romania) from 1960s/1990s to early 2020s.