How much change? An analysis of the initial impact of proportional representation on the New Zealand parliamentary party system

It was to be expected that New Zealand's radical change from a simple-plurality, single-constituency system to a proportional electoral system would produce a multi-party rather than a two-party parliamentary system. Analysis of the mixed-member proportional system's impact on the number and significance of parties, parliamentary cohesion and fragmentation, the power relationship between parties and government, and issue dimensions demonstrates that the impact of the exogenously derived incentives have been moderated by endogenous systemic and institutional forces and, also, by societal characteristics and habits. The brief period since the introduction of proportional representation to New Zealand thus provides an interesting example of how much change can be expected in the short term from electoral system change.