Demography Cheat Sheet
The core ideas of Demography distilled into a single, scannable reference — perfect for review or quick lookup.
Quick Reference
Demographic Transition
A model describing the historical shift from high birth and death rates to low birth and death rates as a society industrializes and develops. It typically progresses through four or five stages, from pre-industrial equilibrium through population explosion to post-industrial stability or decline.
Total Fertility Rate (TFR)
The average number of children a woman would bear over her lifetime if she experienced the current age-specific fertility rates at each age. A TFR of approximately 2.1 is considered the replacement level in developed countries.
Life Expectancy
The average number of years a person can expect to live from a given age, most commonly calculated from birth. It is a summary measure of mortality conditions and reflects public health, nutrition, healthcare access, and socioeconomic development.
Crude Birth Rate and Crude Death Rate
The crude birth rate is the number of live births per 1,000 people per year, while the crude death rate is the number of deaths per 1,000 people per year. The difference between them (natural increase rate) indicates population growth or decline excluding migration.
Age-Sex Structure (Population Pyramid)
A graphical representation showing the distribution of a population by age and sex. The shape of the pyramid reveals demographic history and predicts future trends, ranging from broad-based pyramids in growing populations to column-shaped or inverted structures in aging ones.
Migration
The movement of people across geographic boundaries, either within a country (internal migration) or between countries (international migration). Net migration, the difference between immigration and emigration, is one of the three main components of population change alongside births and deaths.
Dependency Ratio
The ratio of the dependent population (typically those under 15 and over 64) to the working-age population (15-64). It indicates the economic burden on the productive portion of the population and is divided into youth dependency and old-age dependency ratios.
Infant Mortality Rate (IMR)
The number of deaths of infants under one year of age per 1,000 live births in a given year. It is one of the most sensitive indicators of a population's overall health and socioeconomic development.
Urbanization
The process by which an increasing proportion of a population comes to live in urban areas. It involves both the physical expansion of cities and the social transformation that accompanies concentrated settlement patterns.
Population Momentum
The tendency for population growth to continue even after replacement-level fertility has been achieved, because a large proportion of the population is of childbearing age. This demographic inertia means population size responds to fertility changes with a significant time lag.
Key Terms at a Glance
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