From an economic perspective, the fact that some people refuse to be interviewed may be an indication that the survey is more burdensome for them and that therefore the payment of incentives to such respondents (but not others) is justified. Nevertheless, some researchers are concerned that using incentives in this way will be perceived as inequitable by cooperative respondents, and that if they learn of the practice, this will adversely affect their willingness to cooperate in future surveys (Kulka, 1995).
These unintended consequences were the focus of two studies (Singer et al., 1999b; Groves et al., 1999). The first was conducted as part of the Detroit Area Study (DAS), using face-to-face interviews, and the second was done in the laboratory with community volunteers, using self-administered responses to videotaped vignettes.
In the first study, respondents were asked a series of questions concerning their beliefs about survey organization practices with respect to incentives. Three-quarters believed that such organizations offer monetary incentives to respondents to encourage participation (8.9 percent said they did not know). Those who received a prepaid $5 incentive (a random two-thirds of the survey sample) were significantly more likely than those who received no such payment to say that at least some survey organizations use incentives. Indeed, beliefs about this practice appeared to increase with the total amount ($0, $5, $25, or $30) of the incentive the respondent received or was offered, with 94 percent of those who received $30 expressing the belief that at least some survey organizations use incentives.(9)
All respondents also were asked the following question: Some people do not want to be interviewed. However, to get accurate results, everyone chosen for the survey needs to be interviewed. Otherwise, the data may mislead people in the government who use the conclusions to plan important programs that affect everyone. Do you think its fair or unfair for people who refuse to be interviewed to receive money if other people dont? Despite the extensive justification for differential payment included here, 74 percent said they considered the practice unfair.
Near the end of the survey, in a more stringent test of whether the payment of differential incentives was perceived as fair or unfair, a random half of the respondents were informed that because of the importance of including everyone in the sample, some of those who had expressed reluctance to participate had been offered $25, while others had received nothing; they were asked whether they considered this practice fair or unfair. Again, almost three-quarters (72.4 percent) said they considered the practice unfair.