resolution of social inequity, for example, deserves its own instruments. The amount of energy consumed in the future will be determined by economic evolution in the market place, and by events and forces many of which cannot now be foreseen. General directions can be selected for the growth of consumption, but attempts to plot the future in detail are likely to founder on the unexpected cumulative effects of many small decisions. We have attempted here only to sketch possible patterns of growth, and to indicate how these might be affected by various near-term choices.

APPENDIX: A WORD ABOUT GNP

GNP is a composite of many items that mean different things to different people—the summation of apples, can openers, bus rides, homes, and other things. Its calculation is made possible by the use of their market prices, a rough reflection of their economic costs of production in quantities determined by the preferences and purchasing power of consumers. Statistical observation of these quantities and market-balancing prices yields GNP estimates for many nations. It also results in a bias toward items whose prices are determined by the market at the expenses of items, perhaps at least as important, for which no market prices exist

Several corrections have been made or proposed for a more ample concept that expresses aggregate economic welfare. One such attempt, for example, is the recent proposal by Nordhaus and Tobin,50 for a measure of economic welfare (MEW), illustrated by their estimates for 1 year as shown in Table 2-A1.

The corrections and extensions made in this table are of two kinds. Some eliminate the cost of necessary activities that do not directly add to welfare but are aimed at preventing its impairment; these are more correctly regarded as inputs than as outputs. Other corrections add nonmarket activities and uses of time that contribute very substantially to welfare. The economic values of these additions are estimated by the market prices on alternative uses of the time or other resources devoted to these activities.

There is one specifically “environmental” effect in the list of corrections, that for disamenities of urbanization, estimated from the wage differential for comparable work that holds people in the cities. The energy problems that are the focus of the CONAES study involve a great many more environmental effects that are difficult to assess economically. The costs of abating air and water pollution by standards already enforced are included in current GNP estimates as costs of production and consumption. These



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