Contextual Determinants of Electoral System Choice - Ã bo Akademi

and Blais. They also agree that the most basic distinction between different mixedsystems is the presence or absence of a linkage between the tiers, or in Massicotteand Blais’ terminology, whether the application of one formula is dependent on theoutcome produced by the other formula or not. Their classifications of subtypes,however, differ somewhat from each other.Shugart and Wattenberg (2001: 13) point out that most mixed systems tend to leantowards either a majoritarian or a PR system in their overall effects, and the basicsubtypes are therefore called mixed-member majoritarian (MMM) and mixedmemberproportional (MMP). If there is no linkage between the tiers, part of theseats is allocated according to the majoritarian rule, and the remainder isproportionally distributed. The seat allocation or votes cast in the nominal tier doesnot affect the allocation of seats in the list tier, which implies that the overrepresentationof large parties due to the majoritarian rule will also be reflected inthe final seat distribution. Owing to the proportional element, however, themajoritarian boost for large parties will probably not be as large as it would havebeen in a pure plurality/majority election. Therefore, MMM systems are usuallyclassified as semi-proportional systems (see e.g. C. Anckar 2002: 13; Lijphart1999: 145; Reynolds and Reilly 1997: 51-56). In MMP systems, on the other hand,any disproportionality in the nominal tier is corrected in the list tier. As to the finalseat distribution between parties, hence, MMP systems correspond to list PR.An electoral system that has no ambition to correct for any disproportionality in thenominal tier is in Shugart and Wattenberg’s terminology called parallel. Thissystem undoubtedly belongs to the category of MMM systems. Concerning thosesystems in which the tiers are linked to each other, the authors make a distinctionbetween seat linkage and vote linkage. Systems with seat linkage are furtherdivided into compensatory and majority-assuring systems. Systems in which thelist tier compensates parties for the disproportionality obtained in the nominal tierclearly belong to the MMP category. The majority-assuring system, on the otherhand, assures the most successful party in the nominal tier, irrespective of its voteshare, a majority of all seats in the legislature. This formula may also involve anupper limit of seats the winning party may receive. Another peculiarity, appliede.g. in Mexico in the 1988 election, is the application of rules that over-representboth the largest and the smallest parties, and under-represent the medium-sizedparties. This formula may at times be quite proportional but because of the34