Calibration of values in benefit transfer to account for variations in geographic scale and scope: Comparing two choice modelling experiments

Two choice modelling studies in Australia were designed to test for the effects of variations in geographic scale and scope on WTP values. One case study assessed values for improved natural resource management in a river catchment, and the other assessed values for improved protection of the Great Barrier Reef. The results show that increases in the amount of an amenity offered are valued positively and display diminishing marginal utility. Unit value estimates vary inversely with increases in the geographic scope over which an amenity improvement was offered. In the case studies, marginal values for the same unit of environmental improvement could be several thousand times higher when only very small areas were considered compared to when the whole amenity was framed. These results confirm that calibration factors are needed in benefit transfer applications between different geographic scopes. A close inverse relationship was identified between the ratio of quantities involved and the ratio of the WTP amounts. A log-log form of this relationship is recommended as a simple and efficient way of performing this calibration.