This paper reports the results of a statistical summary of estimates of the marginal willingness to pay (MWTP) for reducing particulate matter from hedonic property value models developed between 1967 and 1988. Results using both ordinary least squares and minimum absolute deviation estimators suggest that market conditions and the procedures used to implement the hedonic models were important to the resulting MWTP estimates. The interquartile range for these estimated marginal values (measured as a change in asset prices) lies between zero and $98.52 (in 1982-84 dollars) for a one-unit reduction in total suspended particulates (in micrograms per cubic meter). The mean MWTP is nearly five times the median ($109.90 vs. $22.40), suggesting that outliers are important influences to any summary statistics for these estimates.

This paper reports the results of a statistical summary of estimates of the marginal willingness to pay (MWTP) for reducing particulate matter from hedonic property value models developed between 1967 and 1988. Results using both ordinary least squares and minimum absolute deviation estimators suggest that market conditions and the procedures used to implement the hedonic models were important to the resulting MWTP estimates. The interquartile range for these estimated marginal values (measured as a change in asset prices) lies between zero and $98.52 (in 1982-84 dollars) for a one-unit reduction in total suspended particulates (in micrograms per cubic meter). The mean MWTP is nearly five times the median ($109.90 vs. $22.40), suggesting that outliers are important influences to any summary statistics for these estimates.

In a recent article in this Journal, Cummings al. (1997) offer experimental evidence rejecting the hypothesis that a hypothetical referendum is an incentive‐compatible mechanism for obtaining the social value of, or willingness to pay for, changes in the allocation of environmental goods and services. While cautions in offering a blanket rejection of hypothetical referenda as a means of measuring economic values on the basis of their findings, the authors do suggest that at least in experimental settings respondents appear to behave differently when real money is changing hands. Wheather hypothetical situations adequately mimic real‐market situations has been debated in the contigent valuation literature since its inception (see Cummings, Brookshire, and Schulze 1986). Cummings et al.'s finding of incentive incompatibility appears to offer strong evidence for the critics of hypothetical referenda.