01145pab a2200169 454500 180718b1999 xxu||||| |||| 00| 0 eng d Taagepera, Rein The number of parties as a function of heterogeneity and electoral system 1999 p.531-48 Aug What determines the number of parties in a national assembly? Previous work has emphasized either sociopolitical heterogeneity or electoral system permissiveness, or brought them together on an empirical basis. Here an equation is developed that satisfies two theoretical boundary conditions and expresses the effective number of assembly parties (N) in terms of both the number of politicized issue dimensions (I) and effective magnitude (M) of electoral system: N=I6M15+1. Actually, depending on circumstances, any of the three variables could become the dependent one, affected by the two others. Empirical evidence is presented, based on Lijphart's (1984) data on 22 stable regimes. Reproduced Electoral systems Political parties Comparative Political Studies 44002 44002 44002 0 0 0 0 IIPA IIPA 2018-07-19 Volume no: 32, Issue no: 5 AR44408 2018-07-19 2018-07-19 AR