The paper by John A. List and Craig A. Gallet examines the impact of experimental protocols on the disparities between actual and hypothetical stated values, particularly in the context of contingent valuation methods (CVM). The authors use a meta-analysis to review data from 29 experimental studies, aiming to understand how design parameters influence the magnitude of hypothetical bias. Key findings suggest that subjects tend to overstate their preferences by about a factor of 3 in hypothetical settings. The degree of over-revelation is influenced by factors such as the distinction between willingness-to-pay (WTP) and willingness-to-accept (WTA), the nature of the good (public versus private), and the elicitation methods used. The study addresses several critical questions, including the existence and magnitude of hypothetical bias, the effects of different elicitation methods, and the differences between within-subject and between-subject experiments. The paper also explores whether laboratory and field experiments yield similar calibration functions and whether public goods have larger calibration factors than private goods.The paper by John A. List and Craig A. Gallet examines the impact of experimental protocols on the disparities between actual and hypothetical stated values, particularly in the context of contingent valuation methods (CVM). The authors use a meta-analysis to review data from 29 experimental studies, aiming to understand how design parameters influence the magnitude of hypothetical bias. Key findings suggest that subjects tend to overstate their preferences by about a factor of 3 in hypothetical settings. The degree of over-revelation is influenced by factors such as the distinction between willingness-to-pay (WTP) and willingness-to-accept (WTA), the nature of the good (public versus private), and the elicitation methods used. The study addresses several critical questions, including the existence and magnitude of hypothetical bias, the effects of different elicitation methods, and the differences between within-subject and between-subject experiments. The paper also explores whether laboratory and field experiments yield similar calibration functions and whether public goods have larger calibration factors than private goods.