A Structural Model of Government Formation

The defining feature of parliamentary democracies is the fact that the executive derives its mandate from and is politically responsible to the legislature. This implies that who forms the government is not determined by an election alone, but is the outcome of a bargaining process among the parties represented in the parliament. Furthermore, it implies that the government may terminate at any time before the expiration of a parliamentary term if it loses the confidence of the parliament. Parliamentary democracies, however, differ with respect to the specific rules in their constitutions that prescribe how their governments form and terminate (Lijphart (1984), Muller and Strom (2000), Inter-Parliamentary Union’s archives at http://www.ipu.org). These differences include whether the government needs an actual vote by parliament to legally assume office (the so-called investiture vote), whether the government must maintain the active support of a parliamentary majority in order to remain in office (the so-called positive parliamentarism), whether the rules for tabling a vote of no-confidence require an alternative to be prespecified (the so-called constructive vote of no-confidence), and whether elections have to be held at predetermined intervals (the so-called fixed interelection period).2 1 We would like to thank three anonymous referees and a co-editor for their useful comments and suggestions. Mike Keane, Ken Wolpin, the participants of the “Edmond Malinvaud” seminar at CREST-INSEE, the 1999 Wallis Conference on Political Economy at the University of Rochester, the 2000 meeting of the Research Group on Political Institutions and Economic Policy at Harvard University, the 2001 CEPR Conference on The Economic Analysis of Political Institutions, and seminar participants at Caltech, Chicago, Harvard, Georgetown, Northwestern, and the University of Pennsylvania provided helpful comments. Financial support from the National Science Foundation, and the Weatherhead Center for International Affairs and the Center for Basic Research in the Social Sciences at Harvard University, is gratefully acknowledged. Carl Coscia provided excellent research assistance in the early stages of the project. 2 Parliamentary democracies also differ in their electoral laws. In this paper, we abstract from differences in electoral institutions and restrict attention to parliamentary systems with proportional