All data on voter demographics and voter turnout in German elections are derived from the European Social Survey (ESS), an academic semi-annual cross-national survey of over 30 countries. Interviews are conducted face-to-face and include a minimum effective sample size of 1500 for larger countries and 800 for smaller ones.
We find significant underreporting of voting for the AfD in the European Social Survey (ESS). Only 6.8% of the respondents reported to have voted for the AfD in the last national election while its vote share was 12,6% in the national election. A possible explanation for the underreporting is social desirability bias where respondents believe that voting for the AfD will likely be viewed unfavorably by others. It could also be that AfD voters were less likely than others to consent to being surveyed and sampling weights are insufficient to correct for this sampling bias.
Data on the vote share of right-wing populist parties in national elections in Western Europe were taken from BBC World News.