Oaths and hypothetical bias

Results from experiments using an oath to eliminate hypothetical bias in stated preference valuation are presented. An oath has several potential advantages relative to other methods for reducing hypothetical bias. Our empirical results suggest that with an oath, mean hypothetical payments are not different from mean actual payments and that when controlling for experimental participants' characteristics using regression analyses, the oath eliminated hypothetical bias. •Hypothetical bias is an important problem in stated preference valuation.•Previous methods for eliminating hypothetical bias often do not work well.•Tests a new method for eliminating hypothetical bias – an oath of honesty.•Oath eliminates hypothetical bias and further testing of this method is warranted.