Emigration may be caused by so-called push factors, as when hunger or lack of land “pushes” peasants out of rural areas into cities, or by pull factors, as when an educated villager responds to a job opportunity in the city.
People responding to push factors are often referred to as nonselective migrants, whereas those reacting to pull factors are called selective migrants. Both push and pull forces are behind the rural to urban migration that is characteristic of most countries.