Abstract: In the less-developed rural areas,the idea that the more sons,the happier seems to still have deep influence,and the decreasing land forced many farmers to flow into cities.While in the well-developed cities,young people of marriage age tend to marry late,or even are reluctant to get married.How to understand the relationship between population and economic development? In our country,scholars tend to explain population and economic problems by borrowing the western theory on the relationship between population and economy,therefore it is important for us to have a clear understanding of the origin of the theory.It is of great significance to explore into the phenomenon of “man of excess” and “woman of excess” in the well-developed cities and the economic motivations behind it.

Key words: population, classical economics, &ldquo, man of excess&rdquo, &ldquo, woman of excess&rdquo, enlightenment