Legislators’ voting behavior plays a crucial role in the parliamentary process, both in terms of representation and in terms of accountability. However, two stumbling blocks exist when analyzing legislators’ behavior. The first is the general lack of recorded votes in many parliaments, as well as the non-universality of recorded votes in parliaments that do record votes (Carrubba et al, 2006; Carrubba, Gabel & Hug, 2008; Hug, 2009). Second, the researcher usually lacks good measurements of MPs' policy preferences, which is essential in order to conclude anything with certainty about the extent of the influence of either parties or institutions on voting behaviour (Krehbiel, 1993). In order to address these issues, this paper combines the complete voting records over a 17-year period of the Swedish Riksdag, where all final votes are recorded, with a series of unique surveys of Swedish MPs, with response rates of over 90%, covering five parliamentary terms. In total, nearly 4 million individual voting decisions, made by 942 MPs, are analysed. Further, in order to understand the effect (if any) of electoral incentives on MPs’ behaviour, the paper exploits the change of the electoral system from a closed-list system to a semi-open list system in 1998, using the individual vote totals of MPs as a measure of their ability to get elected independently of their party. This original dataset allows for testing the influence that both policy preferences and electoral incentives have on the legislative behaviour of MPs in a highly institutionalised parliamentary setting, while at the same time allowing for a much improved understanding of what causes both defections and unity in parliamentary regimes. Findings indicate that MPs’ preferences, electoral incentives and whether their party is in government significantly influences their floor voting behaviour.
