What experimental protocol influence disparities between actual and hypothetical stated values?

Preferences elicited in hypothetical settings have recently come under scru tiny, causing estimates from the contingent valuation method to be challeng ed due to perceived ``hypothetical bias.'' Given that the received literatu re derives value estimates using heterogeneous experimental techniques, und erstanding the effects of important design parameters on the magnitude of h ypothetical bias is invaluable. In this paper, we address this issue statis tically by using a meta-analysis to examine data from 29 experimental studi es. Our empirical findings suggest that on average subjects overstate their preferences by a factor of about 3 in hypothetical settings, and that the degree of over-revelation is influenced by the distinction between willingn ess-to-pay and willingness-to-accept, public versus private goods, and seve ral elicitation methods.