本文以綜觀經濟分析法解釋為何名目總需求之變動可能影響實質經濟變量，及如 何估計這影響。這分析法綜合個體，總體，與全面均衡，集中分析一個未必是完全競爭的典 型廠商。有別於（被預知的）名目總需求不影響實質變量的貨幣學派與新古典總體經濟學的 完全競爭的情形，金融危機（尤其是眾所週知的）可能對實質產量造成巨大的影響。這影響 依賴於總需求與成本的外生變化，及一些內生效應，包括需求的價格彈性的變化和成本對廠 商產出、總產出與價格水平的反應。對這些反應的大小之研究，有助於將來對有關影響的估 計。本文也都份解釋經濟預測之困難。

　　　　　This paper uses the method of mesoeconomic analysis to explain why nominal aggregate demand may affect real economic variables and how such effects may be estimated. The method combines micro , macro and simple general equilibrium by concentrating on a not necessarily perfectly competitive representative Hrm. In contrast to the case of perfect competition assumed by the Monecarists and the New Classical Macroeconomists where (known) nominal changes cause no real effects, big changes in output may be caused by a financial crisis, especially if widely known. The effects depend on exogenous changes in aggregate demand and costs, and on endogenous responses including changes in the price elasticity of demand and the response of costs to the firms output, aggregate output, and the price level. Studies on the likely values of these responses will help future estimates of the relevant effects. The analysis also pardy explains the difficulty of making economic forecasts.