An introduction to spatial discounting

Research on the valuation of environmental externalities shows that decision makers tend to discount not only over time but across space. Just as time discounting has implications for intergenerational equity, geographical or spatial discounting has implications for intragenerational equity. Similarly, just as positive time discount rates are warranted by positive net rates of growth of the capital stock, positive spatial discount rates may be warranted by the fact that environmental (or other external) effects of economic activity are diffused at positive rates. This paper introduces the notion of spatial discounting and explores its welfare implications through a simple diffusion model.