Duverger and devolution: a note on the effects of new electoral rules in the UK

Abstract

Elections to the devolved assemblies in the United Kingdom were held under electoral laws distinct from those used for the House of Commons. Comparing the results of the devolved elections using mixed-member proportional (MMP) representation in Scotland and Wales and the single-transferable-vote (STV) system in Northern Ireland to results from the same regions held under plurality rules in UK elections in 1992, 1997 and 2001 provides a quasi-experimental test of Duverger’s Law and Hypothesis. We find support for both mechanical and psychological effects in this comparison and the results indicate that the devolved bodies have more proportional outcomes. The outcomes result in more political parties represented and as a consequence, the single-party majority governments typical in the UK govern none of the devolved assemblies.