Kling, Catherine L.; Bockstael, Nancy

American Journal of Agricultural Economics Vol. 70 no. 3 (November 1988): 654-662.

In practice, it is frequently impossible to identify a single good which is a weak complement to an environmental amenity for which welfare measures are desired. However, a set of goods exhibiting this property sometimes exists, e.g., water-related recreational activities when the nonmarket good to be valued is water quality. A set of weak complements is defined and implications for welfare measurement presented. The proper welfare measure now involves evaluation of a line integral and simple additions of areas under demand curves will not always be correct. However, under certain econometric circumstances, approximate welfare measures can be obtained from estimated functions.