模型是对某种运行系统的抽象和简化设计。经济模型是对经济现实的简化描述。它可以是图式、流程图,也可以是统计表或方程组。经济学上目前倾向于把模型表达为方程组。虽然一些经济模型可以用不同的方式来表示,然而,它们几乎仍然不能象某些科学模型、工程模型或医学模型那样,以三组有型形式来表示。曾经有一段时期,人们对经济系统的水力合 The model is an abstract and simplified design of some kind of running system. Economic model is a simplified description of economic reality. It can be schema, flow chart, it can be statistical tables or equations. At present, economics tends to express the model as a system of equations. Although some economic models can be expressed in different ways, however, they can hardly still be expressed in three sets of formal forms like almost any scientific model, engineering model, or medical model. There was a period of time when people were hydraulically integrated into the economic system