Cover Letter Reduces Response Rate

Abstract

The effect of whether to add or omit a cover letter at written surveys is examined by split-ballot experiments in surveys about victims of a crime in Thuringia (N = 10,184 distributed questionnaires, Austria (N = 804), Switzerland (N = 804) and Germany (N = 1180 + 9787). The survey form is the direct distribution of the questionnaires into the household boxes. The result is that a cover letter reduces the return rate by one tenth. In Austria and Switzerland is the reducing effect of the answering rate even greater. A cover letter discourages younger people from answering. This selection effect causes content distortions and for example, less deviant behavior is indicated. Adding a cover letter reduces the rate of victims by more than 3 percentage points. The omission of a cover letter is more effective in the presented survey form. It saves costs, increases the response rate and does not cause bias effects.