On the Dimensionality of European Union Legislative Decision-Making

Abstract

In this article I test spatial models of European Union (EU) legislative decisionmaking regarding the dimensionality of the policy space. After clarifying the concept of dimensionality, I review the existing literature. I then map out possible ways to test these models based on different dimensionality assumptions. Using quantitative data on actor positions for EU legislative politics, I .rst employ dimension-reducing techniques. The results show that this technique is not appropriate for generating a decreased number of underlying dimensions for the data at hand and that a one- or two-dimensional European policy space cannot be detected. Shifting to more theory-based analysis, I calculate the predicted outcomes for voting models of the EU under different spatial con.gurations. The findings show that the formal models’ predictive power increases with the use of multi-dimensional policy spaces. I conclude by interpreting these findings in the light of a more general debate on evaluating the decision space assumed bymodels of group decision-making.