The research of time lag effect of productivity and GDPbased on GM(1,2) model

With the theory of physics and chemistry, the author constructs a calculating model of productivity which takes production factors as system input and GDP as output. The article puts forward the model about the relationship of productivity, input factors and GDP, and productive forces are activators which transmit all the production factors into GDP. With the calculating model, the article calculates the productivities of world main representative countries such as China, America, France, Germany, Japan, Korea and Thailand from 1971 to 2004. And then the author calculates the fluctuating period of productivity ahead of GDP in these countries with a Time-lag-existing GM(1,2) Model. Through the result, we can find that nearly in all countries GDP are lag productive forces for some cycle which indicates the fact that productive forces drive.