Application of Speculative Valuation Method to Reduce Social Desirability Bias in Economic Valuation of Environment: A Case Study of Recreational Value of Nematabad Dam in Asadabad County of Iran

Despite the development and acceptance of various value extraction methods for public goods and ecosystem services, these approaches may be affected by a number of critical biases causing the results of studies to be different from the real value of resources. The values obtained in hypothetical markets may be affected by Social Desirability Bias (SDB) significantly. This bias is mostly the result of incorporating social traditions and the interviewee's expectations into the answers of questions by other respondents rather than trying to leave truthful answers. This study aimed at investigating the presence of SDB in the economic valuation of the environment through comparing the application of conventional Contingent Valuation (CV) techniques and Inferred Valuation (IV) method. For this purpose, the individual values stated by respondents and their prediction of behaviors of other respondents were compared, focusing on the estimation of the recreational benefits derived from Nematabad Dam Lake in Asadabad County of Iran. The resulting mean willingness to pay (WTP) for recreational value of the concerned lake per visitor (household) in conventional CV technique was estimated by 153,568 IRI rials (US$ 0.56) while in IV method, it was estimated by 116,478 IRI rials (US$ 0.42) for each visit in 2021. A comparison of the calculated WTPs confirmed the presence of overestimation in the CV method, compared with those of the IV method. In other words, a comparison of individual values expressed by respondents and their prediction of other respondents' behaviors would confirm the research hypothesis assuming the presence of SDB in the conventional CV approach.A comparison of the calculated WTPs confirms the presence of overestimation in the CV method compared with the IVM. In other words, a comparison of individual values expressed by respondents and their prediction of behaviors of other respondents confirms the research hypothesis, i.e., the presence of SDB in the traditional CV approach.