Social Desirability Bias in Contingent Valuation Surveys Administered Through In-Person Interviews

This paper presents empirical evidence of mode effects in contingent valuation surveys. We conducted an on-site, split-sample contingent valuation survey of visitors to Fort Sumter National Monument, South Carolina. All respondents were told that the survey was being conducted on behalf of the National Park Service. We find that WTP for a fort visit is approximately 23– 29% higher when the survey is administered through face-to-face interviews with a ballot box rather than being self-administered by the respondent.