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Human Geography Unit 2: Population and migration patterns and processes

Population change follows patterns of fertility, mortality and migration, which geographers explain with models like the demographic transition.

Covers: Population distribution and density, population composition, fertility and mortality, the demographic transition model, population theories, migration types and causes

Study guide

Population is unevenly distributed, concentrated in East Asia, South Asia, Europe and Southeast Asia, often near water and fertile land. Arithmetic density is people per land area, physiological density is people per unit of arable (farmable) land, and agricultural density is farmers per unit of arable land. High physiological density suggests pressure on farmland. Population pyramids show a population's age and sex structure: a wide base means high birth rates, while a narrow base and wide top indicate an aging population.

The crude birth rate (CBR) and crude death rate (CDR) are births and deaths per 1,000 people per year. The rate of natural increase (RNI) = (CBR − CDR) ÷ 10, as a percent. The total fertility rate (TFR) is the average number of children per woman; 2.1 is replacement level. The infant mortality rate measures infant deaths per 1,000 live births. The dependency ratio compares people under 15 and over 64 to the working-age population. The demographic transition model (DTM) describes five stages: Stage 1, high birth and death rates; Stage 2, death rates fall and population grows rapidly; Stage 3, birth rates fall; Stage 4, low birth and death rates; Stage 5, birth rates fall below death rates and population declines. Malthus predicted population would outgrow food supply, while Boserup argued that population pressure drives agricultural innovation. Pronatalist policies encourage births, and antinatalist policies, like China's former one-child policy, discourage them.

Migration is a permanent move. Ravenstein's laws of migration include that most migrants move short distances and that each migration flow produces a counterflow. Push factors drive people away, and pull factors attract them; these can be economic, political, environmental or cultural. Intervening obstacles and opportunities affect moves. Voluntary migration includes chain migration, step migration and transnational migration, while forced migration includes refugees (who cross borders) and internally displaced persons (who don't). Remittances are money migrants send home.

Birth rates fall as countries urbanize and industrialize. Children become costly in cities instead of helping on farms, women gain education and paid work, contraception becomes available and lower infant mortality means families no longer need many children to ensure some survive. An aging or shrinking population creates labor shortages, a smaller tax base and rising pension and health-care costs. Governments respond with pronatalist incentives (parental leave, child payments), immigration or guest-worker programs, raising the retirement age and automation. Japan, Italy and South Korea are common examples.

Carrying capacity is the largest population an area can support without degrading its environment. Technology such as irrigation, fertilizer and high-yield seeds can raise it, which is a key reason Malthus's prediction has not come true globally. Doubling time is how many years a population takes to double at its current growth rate (about 70 divided by the growth rate in percent). It is short in stage 2 and 3 countries with high natural increase and very long or undefined in stage 4 and 5 countries.

The sex ratio compares the number of males to females. Pyramids of developed countries usually show more women than men at the oldest ages because women live longer, while son preference in some countries (for example, under China's one-child policy) has produced more boys than girls at young ages. The epidemiological transition model links the demographic transition stages to changing causes of death. Infectious disease and famine dominate early on, and chronic, degenerative diseases such as heart disease and cancer dominate in later stages. Emerging or returning infectious diseases, like COVID-19, can disrupt this pattern.

Within a country, cities usually have lower fertility and higher life expectancy than rural areas because they offer better access to hospitals, sanitation, education and jobs for women. Raising children also costs more in urban housing. Some governments adopt pronatalist policies to boost the dominant ethnic group's share of the population, an example of ethnonationalism. A strong central (unitary) government can usually enforce population policies more uniformly than a federal system, where regions may resist or implement policies differently.

Key ideas

• Physiological density shows pressure on farmland.
• Population pyramids reveal age and sex structure.
• The demographic transition model links development to birth and death rates.
• Malthus feared overpopulation; Boserup saw it driving innovation.
• Push and pull factors explain migration.

Formulas and rules

Common mistakes

• Confusing arithmetic density (total land) with physiological density (arable land).
• Thinking Stage 2 of the DTM has falling birth rates; death rates fall first.

Words to know

Arithmetic density

People per unit of total land area.

Physiological density

People per unit of arable land.

Agricultural density

Farmers per unit of arable land.

Population pyramid

A graph of a population's age and sex structure.

Crude birth rate

Births per 1,000 people per year.

Crude death rate

Deaths per 1,000 people per year.

Rate of natural increase

Birth rate minus death rate, as a percent.

Total fertility rate

Average number of children per woman.

Replacement level

A TFR of about 2.1, keeping population stable.

Infant mortality rate

Infant deaths per 1,000 live births.

Dependency ratio

Dependents compared with the working-age population.

Demographic transition model

Five-stage model of changing birth and death rates.

Malthusian theory

The idea that population will outgrow food supply.

Antinatalist policy

Policy discouraging births.

Pronatalist policy

Policy encouraging births.

Push factor

A reason people leave a place.

Pull factor

A reason people move to a place.

Chain migration

Migrating to join family or community members.

Refugee

A person forced to flee across an international border.

Internally displaced person

A person forced to move within their own country.

Remittances

Money migrants send to their home country.

Sample practice questions

29 more questions like these, from level 1 to 5, are in the practice set.