Proportional Representation Electoral Systems and Parliamentary Opposition Fragmentation

While proportional representation (PR) electoral systems are associated with considerable advantages, one of their major shortcomings is their limited capacity to concentrate party systems. Compared to fragmented party systems, more concentrated ones tend to feature more direct links between voters and governments, clearer government alternatives, higher degrees of accountability, and higher government stability. For instance, in highly concentrated party systems, the electoral winner can often govern alone or with the support of a small coalition partner. In highly fragmented systems, by contrast, it is to a much greater extent left to the parties themselves to determine which coalitions are formed and which parties are excluded from government. The typically larger number of governing parties in such systems makes it more difficult for voters to identify which party is responsible for which outcomes than in situations where only one or two parties govern together. Multi-party governments are also less stable, as a larger number of actors exist that can bring down the government by withdrawing from the coalition. Whereas the effects of electoral systems on party system fragmentation with regard to governmental outcomes have been studied extensively, research on the consequences for parliamentary oppositions remains rare. Since not only governments but also parliamentary oppositions fulfil essential functions in representative democracies, this neglect is difficult to justify. Especially in parliamentary systems of government, where the executive is often closely connected to the parliamentary majority, it is crucial that oppositions are able to fulfil their control function vis-à-vis the government effectively. While this typically does not require majorities of 50 per cent, specific quorum requirements – such as one third, one quarter, or one fifth – must often be met. Examples include the Slovenian parliament, where one third of MPs is required to establish a parliamentary inquiry committee; the German Bundestag, where one quarter of its members is necessary to file a complaint with the Federal Constitutional Court; and the Dutch Tweede Kamer, where one fifth of MPs is needed to initiate a parliamentary inquiry As with government formation, it is easier for opposition parties to meet such quorum requirements when they can do so on their own or without having to cooperate with an excessive number of other opposition parties. To address this gap in the literature, this paper examines 27 European democracies with PR or mixed electoral systems, focusing on party system fragmentation and its consequences for the functioning of parliamentary oppositions. More specifically, it analyses which levels of fragmentation in the parliaments under study require which forms of cooperation in order to reach these quorum thresholds, and how complex such cooperation is. In measuring complexity, the analysis draws on established coalition theories and primarily considers the number of parties involved as well as their ideological heterogeneity. The proportionality of the electoral system enters the analysis both as a direct explanatory factor, with regard to party system fragmentation, and as an indirect one, with regard to the complexity of opposition cooperation.