Replication Data for: Online Answers to a Postal Survey. A Comparison of Election Surveys in Belgium, 2019-2024

The main advantage of postal surveys is that they allow for a universal initial sampling. It has become standard practice to include an online answering option in those surveys, but a concern about this mixed-mode design remains that not all groups of the population are equally inclined to use this option. In this study, we compare the answering options that were used in two mixed-mode election surveys in Belgium, conducted in 2019 and 2024. Although a larger proportion of respondents now uses the internet option, apart from income we do not find strong indications that elements of stratification have significantly changed. Differences with regard to age however, remain strong as especially older age groups continue to prefer the pen and paper answering option. Our recommendation therefore remains that if one is interested in reaching a representative sample of especially older respondents, providing the pen and paper option does remain important.