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Adriano Pappalardo, "Electoral Systems, Party Systems: Lijphart and Beyond," Party Politics, 13 (November 2007), 721-740.

First paragraph:
As is widely known, Giovanni Sartori (1968: 273) defines electoral systems as 'the most specific manipulative instrument of politics'. This article aims at corroborating the 'manipulations' most typically associated with majoritarian and proportional systems, i.e. their effects on party systems. To date, the best starting point remains Duverger's (1954: esp. 226) distinction between psychological and mechanical effects.1 Voters' decisions reflect in part their perceptions that all systems provide incentives or disincentives for behaviour, thus imposing the need for adaptation to their inherent logics. Psychological effects take place before or at the moment of voting, affecting the decision whether to vote at all and which party to vote for. Mechanical effects occur after the vote, and serve to concentrate the strength of the largest parties. Given the vote, electoral rules determine the distribution of seats, which--according to Duverger (1954: 247, 269, 279, 281-2)--take two fundamentally different shapes: while in plurality systems the distribution disproportionately favours the major parties and thus tends to 'party dualism', or two-partism, proportional representation tends to multipartism, or even to 'multiply' the number of parties. In the ensuing debate, these generalizations, or 'laws', were repeatedly, and convincingly, questioned, but for the present purposes I recall only two crucial amendments.

Figures and Tables:
Table 1. Parties and majorities by formulas, 1945-2002 averages
Table 2. Parties and majorities by thresholds, 1945-2002 averages
Table 3. Regression analysis of electoral systems effects 1: Impact of threshold and assembly size
Table 4. Regression analysis of electoral systems effects 2: Impact of electoral system formula, threshold and assembly size, 1945-2002
Table 5. Number of parties, post-1990 change (%)
Table 6. Regression analysis of electoral system effects 3: Impact of threshold and electoral volatility

Last Paragraph:
(First paragraph of Conclusions) The first of several crucial remarks is that electoral rules condition (psychologically) voters and (mechanically) the parliamentary strength of parties, as well as types of governing majority. The psychological effect, in particular, has proved to be extraordinarily strong, especially if one thinks that voters' decisions are moulded, inter alia, by cleavage structures, party identification, short-term and long-term rational evaluations, and so on. Given so many competing variables, the fact that the electoral system explains up to 53 percent of the variance in the main parties index strongly suggests that we are confronted with the individual condition most powerfully affecting the party systems' format. Thus, Lijphart's previous opposite conclusion should be considered wrong, and not just because he fails to pick up the best available measure (main parties).

Last update November 2013