Thus, all changes in the net benefits producible by a parcel of land, as long as these accrue to the owner of that land, will get capitalized into its price. For example, suppose in an urban area steps are taken by pollution control authorities to reduce the level of air pollution. There is no direct market for clean air; people do not literally buy and sell quantities of clean air. But if cleaning up the air in the community adds $85 per year to the net benefits of living in a house there, the prices of land on which to build house, or of land on which houses already exist, will increase to reflect the capitalized value of these new net benefits. The land prices, in other words, will increase by an amount equal to