摘要：There has been increasing concern that the statistical estimates of the mean willingness to pay (WTP) for public goods may be biased as the statistical method or survey mechanism (as in Contingent Valuation Method, henceforth, CVM) may fail to consider the effects of substitute programs. Economic theory posits that when two or more items are competing for the same limited resource, an increase in expenditure on one, ceteris paribus, reduces spending on the other. So the WTP for a specific program or good depends on what substitutes or complements exist and are considered for that good. Any valuation program that neglects the presence/availability of budgetary substitutes and complements leads to a biased valuation of the public good in question.
