where P(O) is the current price of a trip. The area underneath a demand function and above a price is called "consumer surplus", and it measures the value of making large changes in quantities of trips purchased. Note that the consumer surplus for each individual will depend upon his socioeco- nomic characteristics X and his distance from the site P(O). Individuals who visit the site more often because they have a higher demand function will have a larger consumer surplus. Individuals who face a lower initial price to visit the site will also have a higher consumer surplus. This lat- ter observation leads to an anomaly. Peop- le from further away place a higher value on their trip but place a lower value on the site. Because of the high price of trips, people from further away take far fewer trips and so value highly the few trip However, if the site is lost, they re- trieve the high transportation costs of those few trips and so have little net loss. In order to calculate the recreational val- ue of the entire site, one must sum up the consumer surplus estimates from all ob- served users. The annual consumer sur- plus value of the recreation at a site across all N consume