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Ignacio Lago, "Strategic voting in proportional representation systems: Evidence from a natural experiment," Party Politics, 18 (September 2012), 653-665. [Available at http://ppq.sagepub.com/content/vol18/issue5/ ]

First paragraph:
District-level strategic voting - a vote for a party (candidate) other than the most preferred one in order to avoid wasting the vote on hopeless candidacies in a district - is a crucial but slippery phenomenon in mass elections. First, it affects the party system. As is well known, strategic voting imposes an upper bound, M +1, on the effective number of competitors that will appear in equilibrium, where M is the number of seats to be filled in a district (Cox, 1997). However, measuring strategic voting is not a simple endeavour, given that it entails comparing the actual (or stated) vote with the likely and unobservable vote in a counterfactual situation where incentives for behaving strategically are absent. That is, the so-called fundamental problem of causal inference is particularly acute here (Holland, 1986).

Figures and Tables:
Table 1. Comparing electoral systems in Andalusia
Table 2. Incentive structures for strategic voting in Andalusia
Table 3. Strategic voting in national elections in Andalusia
Table 4. Strategic voting in regional elections in Andalusia

Last Paragraph:
(next to last paragraph) Research on strategic voting agrees on two points. First, strategic voting is crucial for reducing contests with unviable parties or candidates in contests in which at most M + 1 competitors are seriously in the running for seats (Cox, 1997). Second, estimates of the aggregate amount of strategic voting rarely converge, even when researchers examine the same election. To what extent strategic voting is as important empirically as in theoretical models is still an open debate. This paper has dealt with this second point. Using a natural experiment in Andalusia (Spain), where everything is held constant with the exception that in some districts there are very strong incentives for behaving strategically in national elections, but not in regional elections, I have estimated the level of strategic voting in multi-member districts. I found that only a small fraction of the total voters, around 0.75 per cent, behaved strategically in national elections in Andalusia. However, by focusing the analysis exclusively on voters in districts in which they had the opportunity to behave in a strategic fashion, I found that around 9 per cent cast a strategic ballot when presented with the opportunity to do so. Additionally, voters know the different incentives for strategic voting in each territorial level and there are no contamination effects between electoral arenas. Voters did not strategically desert the PCE/IU in regional elections.

Last updated August 2012