What are the main points of Ravenstein's theory of population migration?

Yilong Lu, an associate professor of sociology at Renmin University of China, introduced this in his article: For example, British scholar Ravenstein put forward a theory of population migration in the 1 9th century, and he summarized the law of social population migration as follows:1) Migration is mainly short-distance migration, and long-distance migration is migration to large industrial and commercial centers. Compared with the center that attracts immigrants, the closer the distance, the more immigrants will move in. On the contrary, the farther the distance, the fewer immigrants move in, and the number of immigrants is inversely proportional to the distance. 2) Migration is often staged. As far as a town is concerned, firstly, people from surrounding rural areas move in, and then immigrants from distant rural areas gradually move into the rural areas around the town; 3) Migration flow and reverse migration flow coexist at the same time, but the net migration flow usually flows from rural areas to cities. In general, immigrants who migrate to a region also have reverse migration; 4) Female groups have certain advantages in short-distance migration; 5) The development of transportation, communication and technology has increased mobility; 6) Favorable economic factors are the most important factors to attract immigrants.

American scholar E.S. Lee put forward a more detailed model of immigration law based on Levinstein's theory. He defined immigration as a permanent or semi-permanent change in people's place of residence. He believes that there are four factors related to people's migration and affect migration: first, factors related to migration destination; Second, the factors related to the migration of the original residence; Third, it is related to the factors between the migration destination and the original residence, and fourth, it is related to the individual migrants. In the above four aspects, there are positive factors (+) that are beneficial to migration, negative factors (-) that are unfavorable to migration and ineffective neutral factors (0). The contest and synthesis of positive and negative factors contributed to the final migration.

According to this basic principle, Li further pointed out some laws of population migration: 1) The scale of population migration varies with the differences between the two places, and the greater the natural, geographical and socio-economic differences between the two places, the greater the scale of population migration. For example, between rural areas and cities, the social structure is very different and the migration volume is relatively large. 2) The scale of population migration varies with the structure and characteristics of population groups. Different ages, genders and occupational groups have different immigration volumes. Large-scale migration of population to one direction or destination forms migration flow. 3) The obstacles in the middle are directly related to migration. 4) When a large migration flow is formed, a reverse migration flow will inevitably occur, that is, after a large number of people move out of a certain place, people from other areas move in to compensate. The scale of population migration changes with the change of economic factors. In the period of economic prosperity, the scale of population migration is large, while in the period of economic recession, the amount of population migration is small. 5) Except for special compulsion, the scale and mobility of population migration increase with the delay of time. 6) With the different stages of a country's social and economic development, the scale and rate of migration are also changing.