The fraction of a country's population living in cities follows an attenuated s shape, rising slowly during an initial stage of growth, more quickly during an acceleration stage, then slowing and flattening off during a terminal stage.

一个国家居住在城市的人口比例呈衰减的 S 形，在增长的初始阶段缓慢上升， 在加速阶段上升更快， 然后在末期放缓并趋于平缓。