Unit 2: Population and Migration Patterns and Processes

Rate of Natural Increase (RNI/NIR)

Population growth from births minus deaths (excluding migration), usually expressed as a percent: RNI(%) = (CBR − CDR) / 10.

Demographic equation

Formula for overall population change: (births − deaths) + (immigration − emigration).

Census

A periodic official count of a country’s population that aims to be comprehensive (e.g., age, sex, residence, education, occupation).

Undercount

When a census fails to count some groups accurately (e.g., undocumented migrants, nomadic populations, people experiencing homelessness).

Vital registration

A system that records births, deaths, marriages, and sometimes causes of death; used to calculate fertility and mortality rates.

Sample survey

A data collection method using a subset of the population to estimate patterns for the whole population (often more frequent than a census).

Sampling bias

Error that occurs when a survey sample is not representative of the broader population, leading to misleading results.

Crude Birth Rate (CBR)

Number of live births per year per 1,000 people: CBR = (births in a year / total population) × 1000.

Crude Death Rate (CDR)

Number of deaths per year per 1,000 people: CDR = (deaths in a year / total population) × 1000.

Total Fertility Rate (TFR)

Average number of children a woman is expected to have over her lifetime given current age-specific fertility rates.

Replacement-level fertility

The TFR needed to keep population size stable in the long run (commonly cited as about 2.1 children per woman in many populations).

Infant Mortality Rate (IMR)

Deaths of infants under age 1 per 1,000 live births in a year: IMR = (infant deaths / live births) × 1000; a key indicator of health and development conditions.

Doubling time

An estimate of how many years it takes for a population to double if its growth rate remains constant.

Rule of 70

Approximation for doubling time: Doubling time (years) ≈ 70 / growth rate (%).

Net Migration Rate (NMR)

Immigrants minus emigrants per 1,000 people: NMR = ((immigrants − emigrants) / total population) × 1000.

Arithmetic density

Total population divided by total land area; a broad measure of crowding: population / land area.

Physiological density

Total population divided by arable (farmable) land area; indicates pressure on productive land: population / arable land.

Agricultural density

Number of farmers divided by arable land area; often used as a proxy for farming intensity/efficiency: farmers / arable land.

Ecumene

The inhabited areas of Earth; expands or contracts with technology and economic change.

Population distribution

The arrangement of people across Earth’s surface (where people are located and how they are spread out).

Clustered (nucleated) settlement

A settlement pattern where people live close together, often around resources, marketplaces, or for defense.

Dispersed settlement

A settlement pattern where people live far apart, common in rural areas with large farmsteads.

Population center

An approximate “average location” of a country’s population (population’s spatial balance point) used to track internal migration shifts over time.

Population composition

The characteristics of a population (especially age and sex structure) that shape needs like schools, labor, and health care.

Age structure

The distribution of a population across age groups.

Cohort

A group of people who share a defined demographic trait, often being born in the same time period.

Population momentum

Continued population growth due to a large cohort entering childbearing years, even if fertility rates decline.

Dependency ratio

A comparison of those likely to be economically dependent (commonly ages 0–14 and 65+) to those likely to be working-age (commonly 15–64).

Sex ratio

Comparison of males to females in a population (often stated as males per 100 females); influenced by life expectancy, migration, and social practices/policies.

Population pyramid

An age-sex graph showing age cohorts by sex (typically males left, females right) used to infer fertility, mortality, migration, and future needs.

Demographic Transition Model (DTM)

A model describing typical changes in birth and death rates as societies industrialize and develop (stages shift from high birth/death to low birth/death, with possible natural decrease in very late stages).

Epidemiological Transition Model (ETM)

A model describing how leading causes of death shift with development, generally from infectious/parasitic diseases to chronic/degenerative diseases.

Carrying capacity

The maximum population an area can sustain given resources and technology; not fixed because it changes with innovation, trade, consumption, and governance.

Malthusian theory

Theory that population tends to grow faster than food supply, creating crises unless checked; population can grow exponentially while food supply grows more slowly.

Preventive checks

Malthus’s term for actions that reduce births (e.g., delaying marriage).

Positive checks

Malthus’s term for forces that increase deaths (e.g., famine, disease, war).

Boserup theory

Theory (Ester Boserup) arguing that population pressure can drive agricultural innovation and intensification, increasing productivity and carrying capacity.

Antinatalist policy

Government actions designed to lower birth rates (e.g., contraception access, family planning, incentives for fewer children, raising legal marriage age).

Pronatalist policy

Government actions designed to raise birth rates (e.g., tax credits, paid parental leave, subsidized childcare, housing benefits).

Migration

A permanent or semi-permanent move from one place to another that changes a person’s primary residence and daily-life connections.

Emigration

Leaving a place to move elsewhere (origin perspective).

Immigration

Entering a place from elsewhere to live there (destination perspective).

Push factor

A condition that drives people to leave an origin (e.g., unemployment, conflict, persecution, environmental hazards, high land costs).

Pull factor

A condition that attracts people to a destination (e.g., jobs, higher wages, safety, education, health care, services).

Intervening obstacles

Barriers that make migration harder (e.g., distance, physical barriers, border enforcement, visa rules, travel cost, language barriers).

Intervening opportunities

Closer destinations that are “good enough” to stop further movement, shaping migration routes and corridors.

Chain migration

Migration pattern where later migrants follow earlier migrants from the same origin to the same destination due to social networks that lower cost and risk.

Step migration

Migration that occurs in stages (e.g., rural village → small town → large city → international destination), often reflecting intervening opportunities and resource constraints.

Refugee

A person who flees their country due to a well-founded fear of persecution and is protected under international frameworks.

Internally Displaced Person (IDP)

A forced migrant who flees their home but remains within their country’s borders (does not cross an international boundary).