Comparison of Internet and interview survey modes when estimating willingness to pay using choice experiments

With the increasing use of the Internet as a survey mode, questions of mode effects and how potential effects influence inferences arise. Using a choice experiment combined with mixed logit estimation, willingness-to-pays (WTPs) for attributes are compared between the Internet mode and the more traditional interview survey mode. The results suggest that there are differences in WTP between the two survey models for three of four attributes. Furthermore, WTPs obtained from the interview survey are larger than the WTPs obtained from the Internet survey, suggesting potential social desirability behaviour by the interview respondents. Internet surveys involving sensitive issues may be desirable because of potential social desirability behaviour.