PES: stratified by canton, e.g. individuals were randomly selected within the 26 cantons. A basic sample of around 2600 individuals was calculated for each canton to minimize variance regarding participation and party choice. In the least populous cantons, the samples were increased to ensure that at least 50 individuals could be surveyed. An oversample was taken for the cantons of Ticino and Geneva.
Panel: stratified by big region (NUTS 2), e.g. individuals were randomly selected within the seven major regions (Lake Geneva Region, Espace Mittelland, North-West Switzerland, Zurich region, Eastern Switzerland, Central Switzerland, Ticino).
The samples were drawn from the SRPH by the Federal Statistics Office.