Bold arrow and boxes: factors transforming established party systems.
Dotted arrow and boxes: factors forming new party systems.
ENEC: Effective Number of electoral contestants; ENEP: Effective number of electoral parties; ENPP: Effective number of parliamentary parties.
Institutionally Induced Equilibria: The vast literature elaborating on Duverger’s original insight focuses on the bold boxes 2, 4 and 5. It uses large n, cross-sectional research designs and is able to shows strong co-variation between electoral institutions, strategic voting and party fragmentation in established party systems. (Lijphart 1994; Rae 1967; Riker 1986; Sartori 1968; Taagepera and Shugart 1989) Encouraged by these findings, scholars have tested these same hypotheses in transitional democracies. Some found few differences and, if they did, explained them in terms of additional institutional factors. (Bielasiak 2002; Birch 2001, 370; Birnir 2005; Clark and Wittrock 2005; Golosov 2003; Herron and Nishikawa 2001; Horowitz and Browne 2005, 699; Ishiyama and Kennedy 2001; Jones 1993; Norris 2004, 81-96) Others scholars – especially those considering longitudinal data – found that institutional effects are weaker in transitional than in established party systems. They established that such differences in transitional party systems diminish over time and therefore suggest an important political learning process among voters and politicians. They argued that strategic voting is contingent on prior information about parties’ electoral strength and institutional effects and that