Coalition Agreements and Party Preferences: A Principal Components Analysis Approach

The relationship between coalitions' policies and party preferences is still in need of further study. The few works having explored this issue have used party manifestos to assess how parties influence the policy output of government as expressed in the coalition agreement or in the government declaration. However, the evidence provided has been, at best, mixed. This paper tries to make a twofold contribution to this literature. First, unlike other studies that rely on other techniques, we defend the use of Principal Components Analysis (PCA) as an appropriate method to automatically evaluate how similar/different are the documents measuring party preferences and the coalition agreement without the need of an ideological scaling, and obtain the distances between them. Second, in addition to party manifestos, we also use parliamentary speeches in the investiture debate to capture the preferences of parties. Using data from the Spanish regional coalition governments between 2005 and 2011, we find that i) the use of PCA, which has various advantages, does lead to the emergence of significant relationships between party preferences and coalition agreements, and ii) the use of parliamentary speeches tend to provide more plausible results than manifestos, which signals speeches as relevant documents for the study of coalition dynamics. In particular, we show that being a member of the coalition instead of remaining in the opposition has a decisive influence to lower the distance between the preference of the party and the content of the coalition agreement. Finally, we find that there is a specially strong connection between the candidate speech in the investiture debate and the coalition agreement, which offers promising avenues for further research.