Reliability and Validity in Nonmarket Valuation

We propose a framework for assessing the accuracy of nonmarket values. This involves adapting two widely-used concepts. Reliability addresses variance and validity addresses potential biases. These concepts are formally defined and adapted to assess the accuracy of individual nonmarket valuation studies and the potential accuracy of valuation methods. We illustrate the framework by considering, in a preliminary way, the reliability and validity of the contingent-valuation and travel-cost methods.