Population and Migration: Key Concepts and Models in Demography

Age Distribution

The proportion of individuals of different ages within a population; shows how many people fall into each age group.

Cohort (Age and Sex)

A group of people who share a common demographic trait, usually age or gender (for example, males aged 20-24).

Demographic Transition Model (DTM)

A model that shows how birth rates and death rates change over time as a country develops — from high to low, across five stages.

Dependency Ratio

The number of people who are too young or too old to work, compared to the number of working-age people.

Diffusion of Fertility Control

The spread of birth control methods and ideas (like contraceptives or family planning) across regions and cultures.

Disease Diffusion

The way diseases spread through populations and across space, often following human movement and interaction.

Doubling Time (Rule of 70)

The number of years it takes for a population to double in size, found by dividing 70 by the annual growth rate.

Ecumene

The part of the Earth's surface that is permanently inhabited by humans.

Epidemiological Transition Model

A model describing how causes of death change as a society develops — from infectious diseases to chronic, lifestyle-related diseases.

Infant Mortality Rate (IMR)

The number of babies who die before their first birthday per 1,000 live births in a year.

Malthus, Thomas

An 18th-century economist who argued that population grows faster than food supply, leading to potential famine or crisis.

Mortality

The rate at which people die within a population during a given time period.

Natality

Another word for the birth rate — the number of live births per 1,000 people per year.

Overpopulation

When the number of people exceeds the resources and environment's ability to support them.

Population

The total number of people living in a specific area.

Arithmetic Density

The total number of people divided by the total land area; shows how many people live per unit of land.

Physiological Density

The number of people per unit of arable (farmable) land; shows how much pressure population places on food-producing land.

Agricultural Density

The number of farmers per unit of arable land; shows how developed or efficient a country's agriculture is (lower = more advanced).

Population Distributions

The arrangement of people across the Earth's surface — where populations live and how they are spaced.

Population Explosion

A sudden and rapid increase in population due to high birth rates and falling death rates.

Population Projection

Predicted future population based on current data about births, deaths, and migration.

Population Pyramid

A bar graph showing the age and sex structure of a population.

Rate of Natural Increase (RNI)

The percentage by which a population grows each year, found by subtracting the death rate from the birth rate (ignores migration).

Sustainability

The ability to meet current needs without depleting resources for future generations.

Total Fertility Rate (TFR)

The average number of children a woman is expected to have during her lifetime.

Underpopulation

When there are too few people to make full use of a region's resources or economic potential.

Zero Population Growth (ZPG)

When the number of births plus immigrants equals the number of deaths plus emigrants — population stays stable.

NIC (Newly Industrialized Country)

A country that is transitioning from a developing (agricultural-based) economy to an industrialized one, experiencing rapid economic growth.

MDC (More Developed Country)

A country with a highly developed economy, advanced infrastructure, and high standards of living.

LDC (Less Developed Country)

A country with low levels of industrialization, lower income, and limited access to modern technology and services.

Activity Space

The area within which a person moves during their daily routines and activities.

Asylum

Legal protection granted by a country to someone fleeing persecution, danger, or violence in their home country.

Chain Migration

When people migrate to a location because relatives or members of their community previously moved there.

Cyclic Movement

Repeated or regular movement patterns, such as commuting to work or seasonal travel.

Distance Decay

The decrease in interaction between two places as the distance between them increases.

Forced Migration

Movement of people compelled to relocate by external forces such as war, persecution, or natural disasters.

Gravity Model

A theory predicting migration or interaction between two places based on population size and distance; larger and closer places attract more movement.

Genocide

The deliberate and systematic killing of a specific ethnic, national, or religious group.

Guest Worker

A person who migrates temporarily to another country for employment, often sending money home.

Immigration

Moving into a new country with the intention of living there permanently.

Emigration

Leaving one's country to live in another.

Internal Migration

Movement within a country's borders, such as from one city or state to another.

Intervening Opportunity

A nearer opportunity that reduces the attractiveness or likelihood of moving to a more distant place.

Involuntary Migration

Movement that occurs without a person's free will; another term for forced migration.

Laws of Migration (Ravenstein)

A series of principles stating that migration often happens over short distances, toward urban centers, and usually occurs in steps.

Intercontinental Migration

Movement of people across continents, such as from Asia to North America.

Interregional Migration

Movement from one region of a country to another, like from the rural South to the urban North.

Intraregional Migration

Movement within the same region, such as from a city to its suburbs.

Rural-Urban Migration

Movement of people from the countryside to cities, often seeking jobs and better living conditions.

Migratory Movement

Long-term or permanent relocation of individuals or groups from one place to another.

Periodic Movement

Movement that involves longer stays away from home, such as military service or college attendance.

Personal Space

The physical area individuals claim as their own, which they prefer to keep private and protected.

Place Utility

The perceived value or attractiveness of a place for living, based on personal or economic factors.

Push-Pull Factors

Conditions that cause people to leave an area (push) or attract them to another area (pull).

Refugee

A person forced to flee their country due to conflict, persecution, or disaster and who seeks safety elsewhere.

Remittance

Money that migrants send back to family members in their home country.

Transhumance

Seasonal movement of livestock and herders between lowlands in winter and highlands in summer.

Transmigration

The relocation of people from one part of a country to another, often planned by a government to reduce overcrowding.

Voluntary Migration

Movement undertaken by choice, often for economic improvement, education, or a better quality of life.