# **Causes of Rural-Urban Migration**

An increase in a country's urban population can be due to three causes: the natural growth rate of the urban population, the re-classification of rural settlements as they grow and hit the magic number that makes them cities and towns, and rural-urban migration. Data is generally not available to distinguish among the three, although a 1979 study showed that in 29 developing countries, between 1960 and 1970, about 61% of urban growth resulted from natural growth.<sup>2</sup> More recently, it was estimated that 75% of Mexico's urban growth in the 80s was attributable to natural growth.<sup>3</sup> Of greatest interest to us, however, is rural-urban migration, as this is what is most commonly thought of as "urbanization."

# **_Economic incentives_**

Migration, whether circular, seasonal or permanent, is often a response to economic incentives. The classic analysis of rural-urban migration (Harris and Todaro, 1970) attributes migration to the existence of relatively better economic conditions in urban areas. According to this model, migrants compare expected wages in the city to alternative rural income. If urban wages are higher (perhaps through government wage policies or trade unions), rural people will be attracted to the city. If expected urban income is much higher than rural income, rural-urban migration may occur even if the employment prospects in the city are dim. Migrants may be willing to endure a period of unemployment if expected urban income is sufficiently high (Mazumdar, 1987).

Aside from the higher expected urban income pulling rural people into urban areas, there may be factors "pushing" them out of rural areas. A general decline in agricultural commodity prices since the mid-1970s may have contributed to a decline in rural incomes, which can be highly vulnerable to world market price fluctuations. Increased population density and environmental degradation may also have led to a land shortage among rural peoples, encouraging out-migration (Bryceson and Jamal, 1997). And, of course, higher agricultural productivity in the rural areas releases people and resources for migration into the city, as happened in East Asia.

Rural-urban migration may also follow from a risk diversification strategy. Agricultural income can be highly variable due to changes in climate and rainfall, agricultural market prices, access to land, illness, and war (Bryceson and Jamal, 1997). Some rural household members may migrate to urban areas to reduce family vulnerability to these risks, especially if times of economic adversity in urban areas do not normally coincide with those of rural areas. Many households straddle the rural-urban divide, and

> 2 **This** varied between 38% in Turkey and 74% inSouth Africa where rural-urban migration was restricted. Quoted in Lucas, 1998b prepared for the summer workshop of the 1999-2000 World Development Report. The study is referred to as "Preston, 1979."

> **3** Study by U.S. Bureau of the Census, quoted in Lucas, 1998b 4The Harris-Todaro model has been challenged, both theoretically and empirically. There is however evidence that some migrants move to town and then conduct an employment search.

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