Surveys are a cornerstone of political research, shaping our understanding of public opinion, voting behaviour, and policy preferences. Yet, women are consistently more likely than men to respond "don't know" to survey questions. Existing work focuses primarily on political knowledge, but we know far less about the broader scope and causes of this pattern, including how gender intersects with education, age, class, and ethnicity to shape non-response. Whilst we know, for instance, that the gender gap in political knowledge is much smaller for local, rather than national, issues or on gender-relevant items, we do not understand whether there are similar patterns beyond knowledge questions. This paper provides the first comprehensive, question- and individual-level analysis of survey non-response by gender and intersecting identities, drawing on more than 100,000 respondents across 29 waves of the British Election Study Internet Panel and two novel experiments. We examine how "don't know" responses vary by question type, topic, format, and level of political abstraction, explore potential explanations for these trends, and discuss the consequences for the study of public opinion, policy preferences, and vote choice.
