Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for panel surveys. In one aspect, a method include accessing television history data for viewing devices associated with panelists and that describes, for each viewing device, television advertisements that were presented by use of the viewing device; a proper subset of panelists are selected based on the determinations of television advertisements that were presented and television advertisements that were not presented by use of the viewing device associated with the panelists, and for each of the selected panelists, a survey for the panelist is generated, the survey including one or more questions, each of the questions having been selected based on the television advertisements that were presented and television advertisements that were not presented by use of the viewing device associated with the panelist.