The long and the short of it: Electoral institutions and the dynamics of party system size, 1950–2005

While institutional theories of party system size are usually examined cross‐nationally, there is ample reason to expect that changes in electoral institutions will affect party system size within countries as well. Although some of this effect may occur immediately, most of the effects are likely to be realised over time and across subsequent elections. A series of error‐correction models examine the short‐ and long‐term effects of changes in electoral institutions on party system size. The results indicate that changes in electoral institutions do produce the expected effects on party system size, and that these effects occur mostly over the long term.