The rapid growth of urban areas is the result of two factors: natural increase in population (excess of births over deaths), and migration to urban areas. Natural population growth has been covered in other units, and consequently, here we will concentrate on migration.
Migration is defined as the long-term relocation of an individual, household or group to a new location outside the community of origin. Today the movement of people from rural to urban areas (internal migration) is most significant. Although smaller than the movement of people within borders, international migration is also increasing. Figure 3 shows the annual net international migration totals and migration rates in the world’s major areas between 1990 and 1995. Both internal and international migration contribute to urbanization.
Migration is often explained in terms of either “push factors” – conditions in the place of origin which are perceived by migrants as detrimental to their well-being or economic security, and “pull factors” – the circumstances in new places that attract individuals to move there. Examples of push factors include high unemployment and political persecution; examples of pull factors include job opportunities or moving to a better climate.
Typically, a pull factor initiates migration that can be sustained by push and other factors that facilitate or make possible the change. For example, a farmer in rural Mexico whose land has become unproductive because of drought (push factor) may decide to move to Mexico City where he perceives more job opportunities and possibilities for a better lifestyle (pull factor). In general, cities are perceived as places where one could have a better life, because of better opportunities, higher salaries, better services, and better lifestyles. The perceived better conditions attract poor people from rural areas.