Assumptions and Scenarios
There are many ways to classify sources of resource and environmental pressures. The simplest starts from the proposition that these pressures relate to the throughput of materials in the economy, which is largely determined by total output. Total output, in turn, can be broken down into population and per capita output, giving us two principal determinants of resource and environmental pressures. But the composition of output, the way the output is produced, the way it is used, and where it is used can play equally important roles. Surely, a population that produces throwaway bottles, prefers single-family suburban homes, and relies heavily on private automobiles places vastly more pressure on the environment than one that places less emphasis on packaging and more on apartment living and mass transportation. Moreover, behind these factors are more fundamental ones, like tastes, technology, and labor productivity.
A useful classification of such determinants involves eight different categories. First, of course, are a number of demographic variables such as the size of the population; its rate of growth; its age, sex, and racial structure; and the number and size of households. Such factors can influence the amount and composition of consumption goods purchased, as well as the level of economic activity. Second is output per capita and its principal determinants, labor force participation rates and labor productivity. A third factor might be called the style of living, in particular, preferences for various kinds of goods and ways of using them. The geographic distributionof both population and economic activities is the fourth determinant. The more concentrated economic activities are, the more difficult it is for pollution to be absorbed and assimilated through natural environmental processes; on the other hand, a more dispersed economy requires more resources for transport, housing, and social overhead capital. Next on the list are the technological methods used at each