Elff, Martin. 2022. “The RiLe Index of Party Ideology - A Reductio”.


The RiLe Index based on the data from the Manifesto Project is one of the most widespread measures of parties’ political or ideological positions. Despite being subject to criticism from various authors, it does not seem to have lost in popularity or reputation. Even in 2020 a paper can get published in the American Political Science Review that rests its main argument on this index. There may be a variety of reasons for the continued popularity of this index: (1) that it gives the ”right” results, (2) that its construction is conveniently simple and easy to understand, (3) alternatives often involve complicated substantial and methodological considerations that seem intransparent to most applied researchers, and (4) criticisms usually are buried in appendices of methodological papers that propose alternatives. The paper addresses this situation as it highlights the (implicit) assumptions that justify the construction of the RiLe index and demonstrates some paradoxical implications of these assumptions: The better the fit between these assumptions and reality, the more the RiLe index both exaggerates and occludes the actual movements of political parties. The consequences of these distortions are illustrated by a re-analysis of recent publications. While the MarPor data are an invaluable and irreplaceable source of information about parties’ political positions, the RILE index is clearly not best way to make use of them.

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