The left–right ideological position of individuals is a key variable in political
science, often used to ease the complexities of political preferences into a single
dimension. Despite its widespread use, the single-item left–right scale has faced
criticism for failing to capture the nuanced perceptions of respondents and for being
susceptible to differential item functioning (DIF), where individuals interpret scale
points differently across various contexts. This study investigates the comparability
of the left–right scale across 30 European countries using the anchoring vignette
approach. Data comes from large, nationally representative samples (N = 30,000) collected
through computer-assisted telephone interviews. Respondents were asked to place two
individuals, described as leftist or rightist on a single, 0–11 point left–right scale.
The vignettes focused on the cultural aspects of the left–right concept. Our findings
reveal significant variations in the interpretation of the left–right ideological
scale. The ordering, the mean placements of the vignettes and the average distance
between vignette placements all varied significantly between countries, indicating
substantial cross-national differences in the interpretation of ideological positions.
The findings suggest that the cultural elements of the left–right concept are not
perceived in the same way across Europe. Based on these cautionary results we argue
that researchers employing a single-item left–right scale to gauge ideological positions
in comparative analyses in Europe should consider implementing corrections for measurement
invariance or acknowledge the possibility of varying interpretations.
