Revisiting Incentive Effects : Evidence from a Random-Sample Mail Survey on Consumer Preferences for Fuel Ethanol

This study revisits the issue of monetary incentive effects utilizing data from a mail survey sent to a random sample of adults across the United States regarding preferences for fuel ethanol. The results reported here are consistent with those found in the literature regarding the effect of incentives on response rates: they improved them, with prepaid incentives performing relatively better. We also found that state of residence was significantly correlated with choosing whether to respond to a survey. Regarding the effect of incentives on sample composition, we found that incentives tended to bias the sample in favor of less educated respondents, and tended to attract respondents less familiar with the survey subject. Finally, results indicate that incentives had very little effect on item nonresponse. Instead, item nonresponse was driven by education level, gender, and familiarity with the survey subject. However, combining the findings on sample composition with those of item nonresponse, it appears that the use of incentives indirectly affects item nonresponse by recruiting relatively more respondents that are less educated and/or less familiar with the survey topic, who are then less likely to respond to all questions