AP HG U2

Population Distribution

How people are spread across the Earth. Ex: Most of Earth's population clusters in East Asia, South Asia, Europe, and Eastern North America

Population Density

The number of people per unit area. Ex: Bangladesh is one of the most densely populated countries at ~1,000 people per sq km

Arithmetic Density

Total population divided by total land area. Ex: Egypt's arithmetic density is high, but most people live along the Nile

Physiological Density

Population divided by arable (farmable) land. Ex: Egypt's physiological density is very high because only 4% of its land is farmable

Agricultural Density

Number of farmers per unit of arable land. Ex: Subsistence farming nations like Ethiopia have high agricultural density

Carrying Capacity

The maximum population an area can sustainably support. Ex: Overpopulation in the Sahel region has exceeded the land's carrying capacity

Overpopulation

When a population exceeds the resources available to support it. Ex: Parts of sub-Saharan Africa face overpopulation relative to food supply

Malthusian Theory

Thomas Malthus's argument that population grows faster than food supply, leading to famine. Ex: Critics use famines in Ethiopia to support Malthusian ideas

Neo-Malthusians

Modern thinkers who update Malthus to include resource depletion beyond food. Ex: Concerns about water scarcity in the Middle East reflect Neo-Malthusian thinking

Anti-Natalist Policy

Government policy that discourages births. Ex: China's One-Child Policy (1980–2015)

Pro-Natalist Policy

Government policy that encourages births. Ex: France offers financial incentives for families to have more than two children

Total Fertility Rate (TFR)

The average number of children a woman will have in her lifetime. Ex: Niger has one of the world's highest TFRs at around 6–7 children per woman

Crude Birth Rate (CBR)

The number of live births per 1,000 people per year. Ex: The US CBR is about 11 per 1,000

Crude Death Rate (CDR)

The number of deaths per 1,000 people per year. Ex: Countries with aging populations like Japan have higher CDRs

Infant Mortality Rate (IMR)

Deaths of children under 1 per 1,000 live births. Ex: IMR is very high in sub-Saharan Africa due to limited healthcare access

Life Expectancy

The average number of years a person is expected to live. Ex: Japan has one of the world's highest life expectancies at around 84 years

Natural Increase Rate (NIR)

The percentage by which a population grows, calculated as CBR minus CDR. Ex: Many sub-Saharan African nations have NIRs above 2.5%

Doubling Time

The number of years it takes a population to double at its current growth rate. Ex: A country with a 2% NIR will double its population in ~35 years

Demographic Transition Model (DTM)

A 5-stage model showing how birth and death rates change as a country develops. Ex: The US is in Stage 4; Niger is in Stage 2

Stage 1 DTM

High CBR, high CDR, low population. Ex: Pre-industrial societies; no current countries remain here

Stage 2 DTM

High CBR, falling CDR, rapid population growth. Ex: Nigeria, Afghanistan — death rates drop due to improved medicine

Stage 3 DTM

Falling CBR, low CDR, slowing growth. Ex: India, Mexico — urbanization and education lower birth rates

Stage 4 DTM

Low CBR, low CDR, stable population. Ex: United States, Australia — developed economies

Stage 5 DTM

CBR below CDR, population decline. Ex: Japan and Germany face shrinking populations

Epidemiological Transition Model

Explains how the causes of death shift as countries develop. Ex: Stage 2 countries die from infectious disease; Stage 4 countries die from chronic disease like heart disease

Population Pyramid

A bar graph showing a population's age and sex structure. Ex: A pyramid-shaped graph = young, growing population (Nigeria); rectangular = stable (US); inverted = shrinking (Japan)

Dependency Ratio

The ratio of dependents (young + old) to working-age population. Ex: Countries in Stage 2 have high dependency ratios due to large youth populations

Aging Population

A population with a growing proportion of elderly people. Ex: Italy and Japan struggle economically due to aging populations and pension costs

Migration

The movement of people from one place to another. Ex: Syrians fleeing civil war to Europe

Emigration

Leaving one country to move to another. Ex: Mexicans emigrating to the United States

Immigration

Moving into a new country. Ex: Large-scale immigration from South Asia to the UK in the 20th century

Net Migration Rate

The difference between immigrants and emigrants per 1,000 people. Ex: Germany has a positive net migration rate due to attracting workers from Eastern Europe

Push Factor

A reason that drives someone away from their home. Ex: Drought, war, poverty, persecution

Pull Factor

A reason that attracts someone to a new location. Ex: Job opportunities, political freedom, better climate

Voluntary Migration

Moving by choice. Ex: Moving from Mexico to the US for better economic opportunity

Forced Migration

Moving against one's will. Ex: The Atlantic Slave Trade; Syrians fleeing bombs

Internally Displaced Person (IDP)

Someone forced to move within their own country. Ex: Syrians displaced inside Syria during the civil war

Refugee

Someone who flees their country due to fear of persecution. Ex: Rohingya Muslims fleeing Myanmar to Bangladesh

Asylum Seeker

Someone who requests refugee status in a new country and awaits a decision. Ex: Central American migrants requesting asylum at the US southern border

Intervening Obstacle

A barrier that makes migration more difficult. Ex: The US-Mexico border wall, language barriers, cost of travel

Intervening Opportunity

A closer, attractive alternative that stops migration before reaching the intended destination. Ex: A Mexican migrant stopping in Texas instead of continuing to New York

Ravenstein's Laws of Migration

19th century rules describing migration patterns; most migrants travel short distances, migration happens in steps, and females migrate more locally. Ex: Most migration within Mexico goes to nearby cities before reaching the US

Gravity Model

Predicts migration/interaction between places based on population size and distance. Ex: More people migrate between Mexico City and LA than between a small Mexican town and LA

Chain Migration

When migrants follow the path of earlier migrants from the same community. Ex: Large Turkish communities in Germany formed through chain migration in the 1960s

Step Migration

Migration that occurs in a series of smaller moves toward a final destination. Ex: Moving from a village → small city → large city → another country

Transhumance

Seasonal movement of livestock between pastures. Ex: Herders in the Alps move cattle up mountains in summer and down in winter

Nomadism

Continuous movement with no fixed home, following resources. Ex: Tuareg people of the Sahara follow seasonal water sources

Cyclical Movement

Regular, repetitive movement that always returns to a home base. Ex: Commuting from suburbs to a city daily

Transnationalism

Maintaining connections to both the home country and the new country. Ex: Mexican-Americans sending remittances home while living in the US

Remittances

Money sent by migrants back to their home country. Ex: Remittances make up over 20% of GDP in countries like El Salvador and Nepal

Brain Drain

The emigration of highly educated/skilled workers from a country. Ex: Many Nigerian doctors leaving for the UK, weakening Nigeria's healthcare system

Guest Worker

A legal immigrant allowed to work in a country temporarily. Ex: Turkish gastarbeiter (guest workers) in post-WWII West Germany