Does a QR Code in the Invitation Letter Increase Participation in a Push-to-web Survey?

QR codes are increasingly used in postal invitations to web surveys to facilitate participation. We experimentally tested how a QR code in the invitation letter affects participation in a push-to-web survey of the German family panel (pairfam). The response rate was three percentage points higher with QR codes than without. The QR code effect on response did not differ by gender or education, but it was significantly higher for middle-aged than for younger individuals. Additionally, the proportion of respondents using mobile devices to complete the survey increased substantially. This increase was exclusively due to a 12-percentage-point higher proportion of smartphones, with no increase in the proportion of tablets.