Anchoring vignettes as a diagnostic tool for cross-national (in)comparability of survey measures: The case of voters’ left-right self-placement

There are potentially multiple sources that make it difficult to compare the typical survey measure of the left-right self-placement cross-nationally. Among others, we focus on differential item functioning (DIF) due to the different use of response scales when the left-right is framed as an aggregate dimension of policies, and we examine whether and to what extent the way ordinary citizens make use of the scale is cross-nationally comparable. Our goal is twofold. First, we assess the cross-national comparability of the left-right self-placement scale using the anchoring vignette method in nine European countries. Second, we propose a measure that quantifies the extent of DIF at the country level. The analyses of our original survey and other benchmark studies suggest that the size of cross-national DIF (CN-DIF) in the citizens’ use of left-right scale is relatively small when the left-right concept is considered in policy terms and the comparison is made among Western European countries.