抄録
Economic justification of environmental policy needs some estimation of benefits and cost brought by the policy. Because environmental resources are rarely transacted within a market system, economists have developed methods to elicit people's appreciation for the environment. One of such method is contingent valuation method, which asks how much people would pay for environmental improvement (or need to accept environmental degradation) .
The aim of this article is twofold. First, it examines two major explanations for the disparity between WTP (willingness to pay) and WTA (willingness to accept) observed in contingent valuation survey: Haneman's (1991) substitutability argument, and the endowment effect proposed by Tversky and Kahneman (1991) . We used the Morrison's approach that compensates WTA values to minimize the income effect. Our result supports existence of the endowment effect.
Second, the paper tested the scope insensitivity. Scope insensitivity is the phenomenon that the WTP for larger goods is not significantly larger than WTP for smaller goods. Many researchers regard the issue of the scope as the evidence of shortcomings of the contingent valuation method, but did not fully explain when it can occur. In this study, scope insensitivity was found in some regions of risks, and these regions were different between the endpoint of the risks. This suggests that the scope insensitivity can be affected by the endpoints of the risk. We also found that coefficient of variation was larger when risk was larger. These phenomena show the importance of risk communication by public administrator to assess social benefit and costs adequately.
