Contextual Determinants of Electoral System Choice - Ã bo Akademi

medium size. The other 40 per cent may constitute a single group but it may alsoconsist of several small groups of 5-10 per cent each, which is a completelydifferent situation. Therefore, the category of bipolar fragmentation is introduced.Two criteria apply. First, the level of fragmentation is considered bipolar if the twolargest groups together constitute at least 90 per cent of the population. Second, thelargest group must not exceed 70 per cent of the population. Of course, the extremeconstellation of 70-20 per cent between the two largest groups cannot be regardedas very bipolar, but some generalizations are inevitable when an appropriateclassification is carried out. One could, furthermore, argue that a country in whichone fifth of the population belongs to minorities is not low-fragmented, and that alimit of 90 per cent would be more appropriate as for the category with low levelof fragmentation. Considering the actual level of fragmentation in countries of theworld, the number of countries in which at least 90 per cent of the populationbelong to one cultural group is rather small, especially when all cleavages aretaken into consideration. In this respect, the 80 per cent limit seems reasonable.The categories are as follows:Low level of fragmentation: largest group > 79.9 per centBipolar fragmentation: two largest groups > 89.9 per cent, largest group < 70.1 per centMedium-sized level of fragmentation: largest group between 50 per cent and 79.9 per centHigh level of fragmentation: largest group < 50 per cent, two largest groups < 90 per centAs mentioned, the index of ethnic fragmentation regards ethnicity only, whereasthe index of cultural fragmentation considers all three cleavages equally important.The index runs from 0 to 3, the former representing a low level of fragmentation.For example, a country in which the largest ethnic and linguistic group constitutes95 per cent and the largest religious group 45 per cent of the population scores 0and 3 on the index of ethnic and cultural fragmentation respectively. For countrieswith medium-sized and high level of fragmentation, proportional systems and AVare considered more appropriate than other systems. Similarly, majoritarian (exceptfor AV) and mixed systems are better suited for countries with bipolar or low levelof fragmentation.According to the categorization, medium-sized level of fragmentation denoteshigher fractionalization than bipolar fragmentation. Calculated by Rae’s andTaylor’s index, however, several constellations of medium-sized fragmentation119