Measuring Parties’ Ideological Positions With Manifesto Data

Abstract

Within the rapidly growing literature on positioning political parties along policy dimensions, the rich data series collected by the Comparative Manifestos Project (CMP) has been widely considered as the most systematic and objective source of information. For estimating parties’ positions on the Left—Right dimension alone, several different methods have been proposed which make use of the CMP data. However, unless a new method is proposed, there will seldom be any attempt to check the robustness of the findings across different measurement strategies. In this article, we focus on the parties in Greece, which have been notoriously incorrectly positioned by the ‘standard’ method proposed by the CMP. We contrast the ‘standard’ method with various proposed alternatives and show that the latter outperform the former both in terms of face and convergent validity and in terms of reliability. In addition, we show that this cross-checking is essential, since different methods often lead to diametrically opposite results.