migration

Meaning: Migration is the movement of people from one place to another, usually to live there. Along with births and deaths, it changes a population's size and makeup. Immigration is movement into a region; emigration is movement out of it. Explanations often use push factors (war, persecution, poverty, few jobs) that drive people away and pull factors (jobs, safety, family, services) that attract them. Migration can be internal, such as rural to urban within a country, or international.

Equation: Population change = (births − deaths) + (immigrants − emigrants), where each term is a count of people over a period (persons per year). The second bracket is net migration.

On the MCAT: A passage describes a region gaining or losing residents, and you classify the movement as immigration or emigration, name likely push and pull factors, or predict effects on age structure, urbanization or social change. Some questions ask you to compute or compare net migration.

Common confusion: Immigration and emigration describe one move from two viewpoints. A person is an emigrant from the origin and an immigrant to the destination. Net migration can be positive or negative, so a region with more emigration than immigration loses population through migration. Migration is also not social mobility, which is a change in social position rather than location.