Do They Really Not Know? Survey Mode and Left–Right Self-Placement Responses

Abstract This research note investigates the influence of the survey mode on left–right self-placement using Eurobarometer data (2019–2024; N = 771,804) from 27 European Union countries. We show that people answering the survey via computer-assisted web interviewing (CAWI) provide “do not know” responses significantly less often than those surveyed through computer-assisted personal interviewing. Analysis of respondents surveyed using CAWI reveals negligible cross-country and generational differences in nonplacement, a finding that contrasts with previous studies that did not account for survey mode. Although a large proportion of “do not know” answers might stem from an unwillingness to respond to perceived sensitive questions in face-to-face settings, these differences could also strongly reflect the impact of the survey mode and the specific features of its implementation. Our findings suggest that traditional explanations of nonplacement on the left–right scale need to integrate methodological factors. We provide evidence based on international repeated cross-sectional data that highlights the survey mode as a critical, often overlooked determinant of political self-placement, urging future consideration in comparative survey research.