Spain and Duverger's Law

According to Duverger’s Law, single-member-district plurality electoral systems favor two-party systems, while proportional representation systems tend to create multiple parties.  This however does require the presence of multiple sources of cleavage within the political society: otherwise two parties would form on either side of the only political cleavage.  While Duverger’s law seems correct when applied to the United States, which experiences a two-party system resulting from its use of single-member-district plurality electoral systems, it may be useful to employ the example of another country’s electoral system to see if it also agrees with Duverger’s Law.

The example of Spain and its electoral system serves this purpose.  Spain is currently operating under the Constitution of 1978.  Under that constitution, Spain is a parliamentary monarchy and members of parliament are elected through a system of proportional representation. According to the Inter-Parliamentary Union, Spain utilizes a mixed system: voters choose one blocked party list within the d’Hondt system, but then they also elect single-member constituents by a simple majority vote.

There are many parties in Spain, just as there are in the United States.  However, some are not very effective, while others tend to dominate.  In the Spanish Congress, there are 350 seats available.  These must be distributed among the parties.  The People’s Party represents 45% of the electorate; the Spanish Socialist Workers’ Party represents 29% of the electorate; the United Left represents 7%; the Union, Progress and Democracy Party represents 5%; the Convergence and Union Party represents 4%; and the Amaiur, Basque Nationalist, and Republican Left of Catalonia each represent 1%, while other parties each represent less than 1% of the electorate.

According to the model presented in class, we might first assign 70 seats to the People’s Party and 70 to the Spanish Socialist Workers’ Party; then it would be appropriate to again assign 70 seats to the People’s Party.  We could then assign 18 seats more each to the People’s Party, the Spanish Socialist Workers’ Party, the United Left, and the Union, Progress and Democracy Party.  We could then assign 14 more seats each to the Spanish Socialist Workers’ Party and the Convergence and Union Party, followed by 7 seats for the United Left.  We would then default to assign 4 seats each to the Amaiur, Basque Nationalist, and Republican Left of Catalonia Parties.  Thus, the People’s Party would easily receive the most representation with 158 seats in Congress, while the next most effective party would be the Spanish Socialist Workers’ Party, with 102 seats.  The influence of other parties would be marginal.

Yet because Spain’s system is a hybrid that uses not just closed lists but also simple majorities in single-member districts, there will be opportunity for the remaining 21 seats to be allotted according to popular vote.  In the calculation I’ve presented here, Spain has not allotted seats to any party with less than 1% of the popular vote.  However, Spain has allotted 1 to 2 representatives to a number of parties with less than 1% of the electorate.  Yet the low district magnitude in Spain has led to less proportionate representation.

Sources:
Politics of Spain. Retrieved from http://en.wikipedia.org/wiki/Politics_of_Spain.
Spain. Inter-Parliamentary Union. Retrieved from http://www.ipu.org/parline-e/reports/2293_B.htm.
List of political parties in Spain. Retrieved from http://en.wikipedia.org/wiki/List_of_political_parties_in_Spain.
Spain Election, 2011. Fruits and Votes. Retrieved from http://fruitsandvotes.com/?p=5651.