A quest for innovative environmental policy instruments and a need for policies that harness rather than obstruct market forces has led to "pollution reduction credits" outlined in the 1990 Clean Air Act Amendments. Incentives and management of various pollutants are discussed.

The depletion of forested wetlands is a pressing environmental concern, but has wetland depletion and conversion to agricultural cropland been excessive? A dynamic analysis of resource exploitation in the presence of environmental consequences is required. The structure and parameters of a model of socially optimal wetland use are found to bear a well-defined relationship to those which emerge from a private-market model of wetland exploitation, providing a basis for internalizing environmental externalities and for identifying optimal resource-exploitation strategies. Empirical analysis focuses on the area of severest wetland losses in the United States, the Lower Mississippi Alluvial Plain.

By affecting relative economic returns, public infrastructure investments can induce major changes in private land use. We find that 30 percent of forested wetland depletion in the Mississippi Valley has resulted from private decisions induced by federal flood-control projects, despite explicit federal policy to preserve wetlands. Our model aggregates individual land-use decisions using a parametric distribution of unobserved land quality; dynamic simulations are used to quantify the impacts on wetlands of federal projects and other factors.

This paper documents an analysis of English demographic change over the period 1573–1873. A simultaneous equations model is developed in order to test four alternative demographic theories—the constant equilibrium wage theory, the constant fertility theory, Lee's original (1973) synthesis theory, and a new, composite theory. Each is a special case of a general demographic model which provides both for exogenous technological change and for endogenous migration behavior. Two-stage least-squares estimation yields parameter estimates and test statistics, which provide evidence of the superiority of the composite theory of demographic change. By statistically affirming the composite theory of demographic change, this paper confirms that the mortality level played a dominant role in English demographic change during the preindustrial period. The analysis also provides support, however, for the classical notion that shifts in the labor demand function were a dominant cause of long-run population changes, subsequent to the beginning of British industrialization.