A Comparative Study On The Methods Of Population Projection

The method of regional population projection already has more than300years old from the establishment to the present. From the early simple manual calculation to today’s complex mathematical models, there are many kinds of forecasting method coming from this subject area, such as the forecast method of statistics and demography, each forecast method has its own advantage for developing. The scenario projection method is a kind of famous population forecast method in the field of demography. In the meantime, this is the best standardized forecast method adopted frequently by the United Nations because of its high accuracy. Population cohort is the foundation of the model, and then the researcher could conjecture relevant variables of the target year by the way of population-shift algorithm step by step. As a matter of fact, the scenario means that if the result of population projection were certain, relevant variables should be divided into different parts because of some various assumptions, meanwhile the trend of population development will go on moving toward a certain direction if one assumption is available. Just like mathematical method, therefore, total population can be forecasted by the scenario projection method. But other than that, the fertility and mortality, migration and demographic structure are forecasted as well with this method.There are five chapters in this paper, a case in point that Chinese population will be mainly forecasted with scenario projection method and total population forecasted with mathematical method will also be presented in some chapters, after that the result of population projection will be split into three scenarios, there are high variant scenario, medium variant scenario and low variant scenario. The trend of Chinese future population size on the basis of the previous studies will be presented in order to provide reference for establishing the nation’s population policy and promoting its economic development. To begin with, the concept of population forecasting and methods are essential, the domestic and foreign research results on population projection and scenario projection are referred in chapter one. The procedure of model establishment is the key of scenario projection, including the core formula of population-shift algorithm, life expectancy, total fertility rate, sex ratio at birth, fertility pattern and so on. Based on the data of population cohort of the sixth national population census in2010, what’s more, the changing trend of total population, aging population, population between0and14years old, labor suitable population, women of reproductive age and all the coefficients are forecasted with scenario projection method between2011and2050, and then three scenarios are presented and the medium variant scenario is more suitable for Chinese situation. Chinese total population, once more, is forecasted with some common mathematical models of the regional population projection and combined with scenario projection method, the three scenarios are given as well. As a reference, Chinese population will have a higher likelihood of growing to about1.5billion in2050forecasted with mathematical models. Maybe, the predictions of the low variant scenario of Logistic model and Gompertz model will be less than1.5billion.Finally, combined with the merits and faults of all models and Chinese situation, we find that effects of scenario projection method are better than other methods for medium and long term prediction. Consequently, China’s population is aging fast and the situation will be more serious than we can imagine. The coefficient of aging population will reach up to25percent, women of reproductive age, population between0and14years old and labor suitable population will decrease continuously and total social dependency ratio will increase to70percent in2050. By then, Chinese total population will increase to1.38billion in the medium variant scenario. Certainly, if it is true that Chinese total population has a rising trend by the middle of the century which forecasted with mathematical models, a population of more than1.5billion is possible.