The interactive effects of monetary incentive justification and questionnaire length on mail survey response rates

An experiment was conducted in which a survey questionnaire and a $1.00 incentive were sent to 200 randomly selected residents of a midwestern city. For half of the respondents, the enclosed monetary incentive was justified in a cover letter as an attempt to induce feelings of obligation to return the questionnaire (equity‐salient condition), whereas for the other half of the respondents, the incentive was justified as an appreciative gesture (standard condition). Furthermore, some subjects received a short questionnaire, whereas the rest received a long questionnaire. Response rates were assessed by condition. As predicted, the equity‐salient appeal produced a significantly higher response rate than the standard appeal, but only for subjects who received the short questionnaire. Results are discussed in terms of personal equity theory.