按照美国著名的发展经济学家迈克尔·P·托达罗的人口流动模型,作为一种经济现象的人口流动基本上是按城市和乡村预期收入而不是实际收入的差别进行的,“预期收入是按农村和城市工作之间的实际收入差距和一个新移民得到城市工作的可能性来衡量的”,“劳动者把他们在一定时间内城市部门预期收 According to the demographic transition model of the famous American development economist Michael P. Todaro, the population flow as an economic phenomenon is basically based on the difference between the expected income and the actual income in rural areas rather than the actual income. “The expected income is Measured by the actual income gap between rural and urban jobs and the likelihood that a new immigrant will get a city job ”," The workers treat them as expected in the urban sector for a period of time