The Comparative Manifestos Project (CMP) data are the most popular source for parties' positions on the left-right and other ideological and policy dimensions. Over the past few years, several researchers have identified various methodological problems in the CMP data, but third-party users rarely acknowledge them.This article classifies the problems associated with the CMP into four areas: (1) theoretical underpinnings of the coding scheme; (2) document selection; (3) coding reliability; and (4) scaling. The article reviews each area systematically and concludes with a set of recommendations regarding the use of the CMP data. bs_bs_banner

The past few years have seen the advent and proliferation of Voting Advice (or Aid) Applications (VAAs), which offer voting advice on the basis of calculating the ideological congruence between citizens and political actors. Although VAA data have often been used to test many empirical questions regarding voting behaviour and political participation, we know little about the approaches used by VAAs to estimate the positions of political parties. This article presents the most common aspects of the VAA approach and examines some methodological issues regarding the phrasing of statements, the format of response scales, the reliability of coding statements into response scales and the reliability and validity of scaling items into dimensions. The article argues that VAAs have a lot of potential but there is also much space for methodological improvements, and therefore concludes with some recommendations for designing VAAs.

A B S T R A C TWithin 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.KEY WORDS Ⅲ ideology Ⅲ left-right Ⅲ party manifestos Ⅲ reliability Ⅲ validity P A R T Y P O L I T I C S V O L 1 6 . N o . 4 pp. 427-450

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This paper considers the issue of document type diversity in the Comparative Manifestos Project (CMP). For many years the CMP has been collecting and coding a variety of documents, such as speeches, pamphlets, newspaper articles and leaflets, as manifesto proxies. By using previously unexplored archival material to perform controlled comparisons between different types of documents, this paper argues that the coding of such documents introduced considerable measurement error to party position estimates. Statistical analyses indicate that this measurement error is systematic rather than random as it is often manifested as centrist bias in parties' left-right position estimates. Consequently, the paper argues that random error correction methods cannot always correct for error attributed to the coding of proxy documents. The paper concludes with some recommendations for thirdparty users of the CMP data and documents and a plea to the CMP research team.