Contextual Determinants of Electoral System Choice - Ã bo Akademi

territorial organization and chamber structure have no influence on electoralsystem choice in any comparison. Neither is population size nor cultural diversitysignificantly related to the dependent variable, although the effect of culturaldiversity comes rather close to the 0.05 level. Again, the adoption of pluralitysystems is associated with British and French colonial legacy – the latter withregard to the comparison between plurality and PR. However, it should be pointedout that the associations are not very strong. In contrast, the adoption of mixedsystems and the unpopularity of plurality systems is strongly related to temporaldiffusion during the fourth period. The model also emphasizes the importance ofregional diffusion in explaining the adoption of proportional systems. As inprevious models, no variable explains anything when majority and mixed systemsare compared with each other. The double-checking with four binary logisticregressions confirms these findings.Normally, a final model that constitutes a parsimonious compromise is lastlypresented. In this case, the most parsimonious model would consist of Britishlegacy, French legacy, regional diffusion and the fourth period, i.e. a model verysimilar to the first model. When the second and the third period are excluded fromthe first model, the model chi-square value (122.1) and the Nagelkerke value(0.394) are only modestly affected, while the –2 Log likelihood value isconsiderably improved from 133.4 to 78.7. In comparison with table 8.1, the mostparsimonious model strengthens the significance of temporal diffusion in thefourth period. British legacy, and to e lesser extent French legacy, are still relatedto the introduction of plurality systems, whereas regional diffusion is associatedwith the adoption of proportional systems.As a whole, these four variables explain electoral system choice in the totalpopulation. None of the other independent variables are significantly related toelectoral system choice in any comparison. In general, the effect of French legacyis weaker than the effect of British legacy, regional diffusion and temporaldiffusion. The importance of temporal diffusion is confined to the frequentadoption of mixed electoral systems and the decline of plurality system choices inthe fourth period from 1990 to 2003.217