The European Social Survey is a high quality cross-national survey of attitudes and values, carried out in between 20 and 30 countries every two years. The project started formally in 2001 but was many years in the making. The ESS was initiated and seed-funded by the European Science Foundation, the body representing almost all of Europe's main national academic funding agencies.
Data is collected face-to-face, using either Computer Assisted Personal Interviewing (CAPI) or Pencil and Paper Interviewing (PAPI).
Each country must draw a probability sample. Where possible, survey agencies use a register of individuals as their frame; where this is not possible a file of addresses is used and selection of respondents made on the doorstep.
Each country aims for an effective sample size of 1500. This is based on the assumption of a simple random sample of 1500 individuals. Where the sample design deviates from this model, for instance through the use of geographical clustering or the use of stratification, the actual number of interviews is increased to account for this.