Unexpected effects of a prior feedback letter and a professional layout on the response rate to a mail survey in Geneva.

Obtaining high response rates in mail surveys is always a challenge. Several methods have been proposed to increase response. Sending partici pants a letter a few days before the question naire was effective in some studies12 but had a negative impact in another.3 Giving special attention to the questionnaire layout was also effective,4 although the effect was not always very important.2 We tested whether a prior feedback letter and an attractive questionnaire layout increased the response rate to a postal health survey conducted in Geneva, Switzer land, in 1994.