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. 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. We also examine whether and to what extent ordinary citizens' 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 used in nine European countries. Second, we propose a measure that quantifies the extent of DIF at the country level. Our original survey and other benchmark studies suggest that the size of cross-national DIF (CN-DIF) in citizens' use of a left-right scale is relatively small when the left-right concept is considered in policy terms and when a comparison is made between Western European countries.