【单选题】

Formal economic forecasting is usually based on a (1) theory as to how the economy works. Some theories are complicated, and their application requires an elaborate (2) of cause and effect. Others are relatively simple, (3) most developments in the economy to one or two basic factors. Many economists, for example, believe that changes in the supply of money (4) the rate of growth of general business activity. Others (5) a central role to investment in new facilities-- housing, industrial plants, highways, and so forth. In the United States, where consumers (6) such a large share of economic activity, some economy believe that consumer decisions to (7) or save provide the principal (8) to the future course of the entire economy. Obviously the theory that a forecaster applies is of (9) importance to the forecasting process; it (10) his line of investigation, the statistics he will regard as most important, and many of the techniques he will apply.

Although economic theory may determine the general (11) of a forecast, judgment also often plays an important role.A、forecaster may decide that the circumstances of the moment are (12) and that a forecast produced by the (13) statistical methods should be modified to take account of special current circumstances. This is particularly necessary when some event outside the Usual run of economic activity has an a (14) economic effect. For example, forecasts of 1987 economic activity in the United States were more accurate when the analyst correctly foresaw that the exchange value of the dollar would (15) sharply during the year that consumer spending would slacken, and that (16) rates would rise only moderately. None of these conclusions followed (17) purely economic analysis; they all required judgment as to future decisions (18) , an economist may decide to adjust an economic forecast that was made by traditional methods to take account of other unique (19) ; he may, for example, decide that consumers will (20) their spending patterns because of special circumstances such as rising price of imports or fear of threatened shortages.
A．waste
B．invest
C．purchase
D．economize