The Effects of Material Incentives in Mail Surveys: Two Studies

Two studies were undertaken on the effects of including a material nonmonetary incentive in mail surveys, using various samples of the general public in the Netherlands. The results show that nonmonetary incentives produce a higher initial response rate, but follow-ups reduced the effect of the incentive to a nonsignificant ratio. Inclusion of the incentive produced no response bias and little volunteer bias. Results from these studies offer a possible explanation for why past studies on nonmonetary incentives have often shown positive effects: they were conducted using methods that produced low response rates. When methods that produce high response rates are used, the effect of nonmonetary incentives on response rate disappears. Finally, the use of monetary incentives in mail surveys with a high base response is discussed.