The Improved Method Based On Population Forecast

The population system is a dynamical system. The trend of a population will affect the development of the society and its economy. The age structure is one of the most important indexes in population research. The forecast of age structure plays an important role in making population policies.The Grey GM (1,1) model, Optimization GM(1,1) model and the GM(1,1) model which is gainded by the least square method were applied in forecasting the total population in short time in China. All the age structure population models are the population evolution equations which are established by Song Jian. In order to forecast the age and sex structure easily, the author used the discret model as the primarily model. Compares with the equation of continuity, discrete model's merit is that the programming is convenient, it is easy to circulate the iteration. Its parameter matrix and the vector number of lines and the population age correspond, the direct input statistical data can be carried on the computation.In the population system model, there were several important parametric functions. These function enormously influence the population evolution equation's result. How to obtain the parametric function, is also the key point of this article. Regarding the mortality rate function, because the mortality rate change is been influenced by the outside enormously. It is difficult to seek the rule that the age mortality rate is unstable. Is also fits very difficultly with the existing mathematical model establishes the forecast model. Because this article according to 2001-2005 year statistical data to use the weaken the derived law to obtain the mortality rate in the future. Its model precision is higher than the sole mortality rate function. This method soluted the mortality rate only to consider in the theory. It had its limitation. It had not related the tangible impact mortality rate factor. However the mortality rate influencing factor has many, because contacts the material is limited, This article also can only unify most main influencing factor - average per person GNP. It is that Liang Hong proposed promotes in the minute age section mortality rate forecast take the average per person gross national product as the independent variable regression equation. And used China population statistic data to confirm this model feasibility. This article has established the fertility rate separately in the population evolution equation's foundation, models and so on mortality rate. These models may be applied alone. And, the fertility rate and the mortality rate model not only used for describing the fertility rate and the mortality rate along with the ageing change tendency, but may also divide the age group data to return to original state into minute age other data. Therefore, this article establishes each sub-model is in itself studies the birth question as well as the death question effective mathematical instrument.Regarding to population migration function, because the material is limited, it is unable to obtain the population transport number and according to the age section population transport number, therefore when we use the population evolution equation carried on the population forecast and the analysis, we can not give the consideration temporarily. In the later work, we need to obtain in detail according to the age population migration data further, establishes the population migration function, leads in the population development function, carries on the population forecast and the population state analysis.Each model in this article may calculate the majority of target population, including aging of populations, average fertility rate, data and so on mortality rate. In government policy making time, these models may play the reference role. For example through the change average fertility rate, we may carry on the control to the population aging, will carry on the control to the future population. Changes the average per person gross national product, under the quite different economic growth rate the population age structure are different, thus we can analyze which kind of development speed t is more reasonable.