Trend method: according to the statistical data of the past population and assuming that the future population trend still develops according to the same function curve, the future population can be estimated. Commonly used population development functions are: geometric development function, exponential development function, modified exponential development function, Lauderstie curve and Gomez curve. This method is based on a certain mathematical function, so it is also called mathematical method.

Factor analysis: This is a widely used forecasting method in modern times. It requires the population to be studied to have more detailed statistical data, such as population by age and sex, fertility rate, mortality rate and so on. When forecasting urban and rural population and regional population, it is also necessary to obtain the relevant information of population migration. According to these data, we can estimate the future changes of fertility and mortality, and then predict the changes of population size and structure. The mathematical model used in factor analysis can be deterministic or probabilistic, and can be combined with special needs for prediction and calculation, such as economic population prediction and talent prediction. The population forecasting model can be continuous or discrete. Generally speaking, in order to run on the computer and conform to the caliber of demography, discrete population forecasting models are often used.