说明：  人口模型是描述一国或地区人口总量和结构变动规律的系统动力学模型。总人口和出生人口数形成一个正反馈回路,它决定总人口的增长。
(The population model is a system dynamics model which describes the change law of the total population and structure of a country or region. The total population and the number of births form a positive feedback loop, which determines the growth of the total population.)