Legislators'' preferences regarding party unity: An institutional comparison of old and new democracies

Despite the key role played by party unity in legislative voting in Europe, it is little understood. European legislatures display almost uniformly very high levels of party voting unity (Sieberer 2006), but the reasons for this remain unclear. One major hypothesis argues that the extent to which MPs have incentives to cultivate a personal vote determines levels of party unity (Carey & Shugart 1995), but the evidence for this is mixed. In order to test this hypothesis, this paper will seek to explain what determines levels of party unity from the perspective of individual MPs. This paper will not look at roll-call voting data, as it suffers from grave problems of selection bias in most European countries (Carrubba et al. 2008; Clinton & Lapinski 2008; Hug 2010), as well as extremely low levels of variance on the level of individual legislators. Rather, this paper will approach the issue from the analysis of surveys of parliamentarians. More specifically, it will analyze what determines the preferences parliamentarians hold when it comes to party unity, looking at both institutional (electoral incentives, threat of early elections, government status) and individual (preferences, socialization) factors. Further, the use of surveys will allow me to control for preferences, a key factor that is too often left out of legislative research (Krehbiel 1993 – for an excellent exception, see Kam 2001, 2009). The paper will compare the attitudes of two sets of very different systems: The Nordic countries, and four Central European countries in the period of democratic consolidation in the early 1990’s. Thus, it will allow for a comparison not only across similar systems, but also across very different systems. By comparing newly democratic parliaments with some of the most strongly institutionalized parliaments, structural effects can be confidently assessed.