We examine whether propensity to participate in a web-CAPI mixed-mode survey is influenced by being contacted by email in addition to mail. In panel surveys, researchers can ask at each wave for an email address, but there is little evidence regarding the value of doing so. Using data from a...

Mixed modes (MM) are receiving increased interest as a possible solution for saving costs in panel surveys, although the lasting effects on data quality are unknown. To better understand the effects of MM on panel data I will examine its impact on random and systematic error and on estimates of...