Population and Migration Patterns and Processes
Unit 2 of AP Human Geography, worth 12–17% of the exam. 14 questions below, each with the working. Every answer was checked by a second pass before it was published.
Population distribution and density, population composition, dynamics and growth, the demographic transition model, population policies, causes and effects of migration.
How this unit is tested
Start by sorting every prompt into one of six buckets: distribution/density, composition (pyramids, sex ratio, dependency ratio), growth dynamics (CBR, CDR, NIR, TFR, doubling time), the demographic transition model, population policy, or migration. AP questions in this unit are heavy on data interpretation, so before you answer, identify what numbers or graph you've been given and what formula or model actually applies to them — a population pyramid answers composition questions, not density questions.
For calculation questions (density, dependency ratio, NIR, doubling time), write the formula down first, then plug in numbers, then sanity-check the result against what you know about real countries — a dependency ratio of 100 or an NIR above 3% should signal a Stage 2 country with a youthful population, not a mistake in your arithmetic.
For the demographic transition model, don't just memorize stage numbers — memorize the birth rate and death rate behavior in each stage, because pyramid shapes and NIR values are just consequences of that behavior. Pair the DTM with the epidemiological transition model, since the two move together: as death rates fall in Stage 2, the leading causes of death shift from infectious to degenerative disease.
For migration, always separate the push factor (something driving someone from the origin), the pull factor (something drawing them to the destination), and any intervening obstacle or intervening opportunity that changes the outcome. When asked about effects, split them into origin effects (brain drain, remittances, reduced population pressure) and destination effects (labor supply, cultural diffusion, strain on services) rather than listing effects generically.
What you have to know
Demographic Transition Model (DTM)
A model describing four (sometimes five) stages a country passes through as it develops: Stage 1 (high birth rate, high death rate, low natural increase), Stage 2 (high birth rate, rapidly falling death rate, high natural increase), Stage 3 (falling birth rate, low death rate, moderate natural increase), Stage 4 (low birth rate, low death rate, near-zero natural increase), and Stage 5 (birth rate falls below death rate, negative natural increase).
Dependency Ratio
Dependency ratio = [(population under 15 + population 65 and older) ÷ population aged 15–64] × 100; it measures the economic burden on the working-age population, with higher values indicating more dependents per worker.
Malthusian Theory
Thomas Malthus argued that population grows geometrically while food supply grows only arithmetically, so population will eventually outrun food supply unless checked by famine, disease, war, or moral restraint.
Ravenstein's Laws of Migration
A set of generalizations including: most migrants move only a short distance (distance decay); migration occurs in a series of waves toward large cities; long-distance migrants tend to move to major urban centers; most migration is rural-to-urban; and each migration flow produces a counterflow.
Push-Pull Migration Model
Migration decisions result from push factors that drive people away from their origin (e.g., conflict, unemployment) and pull factors that attract them to a destination (e.g., jobs, safety), modified by intervening obstacles (barriers to movement) and intervening opportunities (a closer, adequate alternative destination).
Epidemiological Transition Model
A model paired with the DTM describing how leading causes of death shift as a society develops: from infectious/parasitic disease (Stage 1–2) to degenerative and human-created diseases (Stage 3–4), and potentially to a resurgence of infectious disease in Stage 5.
14 practice questions
-
A country has a population of 12 million and 400,000 square kilometers of arable land. What is its physiological density?
Show the answer
Answer. 30 people per square kilometer of arable land
Physiological density = total population ÷ arable land area = 12,000,000 ÷ 400,000 = 30 people per square kilometer of arable land. This measures pressure on farmland, unlike arithmetic density which would use total land area instead. -
Which of the following best distinguishes physiological density from arithmetic density?
- Physiological density counts only urban population, while arithmetic density counts total population
- Physiological density uses only arable land as the denominator, while arithmetic density uses total land area
- Physiological density is always higher in wealthy countries
- Arithmetic density accounts for population growth rate while physiological density does not
Show the answer
Answer. Physiological density uses only arable land as the denominator, while arithmetic density uses total land area
Arithmetic density divides total population by total land area, while physiological density divides total population by arable (farmable) land only, making it a better measure of pressure on food resources. -
A country has a population where 30% are under 15, 60% are aged 15–64, and 10% are 65 or older. Calculate the dependency ratio.
Show the answer
Answer. About 67 dependents per 100 working-age people
Dependency ratio = [(30 + 10) ÷ 60] × 100 ≈ 66.7, meaning roughly 67 dependents for every 100 people of working age. -
A population pyramid with a very wide base that narrows rapidly moving up, indicating high birth rates and a young overall population, is most typical of which DTM stage?
- Stage 1 (High Stationary)
- Stage 2 (Early Expanding)
- Stage 4 (Low Stationary)
- Stage 5 (Declining)
Show the answer
Answer. Stage 2 (Early Expanding)
In Stage 2, death rates fall sharply due to improved sanitation and medicine while birth rates remain high, producing rapid natural increase and a wide, expansive pyramid base of young dependents. -
According to Ravenstein's laws of migration, what pattern do most migrants follow regarding distance?
- Most migrants move directly to another continent
- Most migrants move only a short distance, a pattern known as distance decay
- Migration distance is unrelated to the number of migrants
- Most migrants move to rural areas rather than cities
Show the answer
Answer. Most migrants move only a short distance, a pattern known as distance decay
Ravenstein observed that migration volume decreases as distance increases (distance decay), and that most migrants relocate relatively short distances rather than undertaking long international moves. -
Which of the following is an example of a pull factor in migration?
- Civil war in the country of origin
- Higher-paying job opportunities in the destination country
- Drought destroying crops at home
- Religious persecution in the home country
Show the answer
Answer. Higher-paying job opportunities in the destination country
Pull factors are positive conditions at the destination that attract migrants, such as job opportunities; the other three options describe negative origin conditions, which are push factors. -
Why is a total fertility rate of 2.1 often called 'replacement-level fertility'?
Show the answer
Answer. Because it is roughly the number of children per woman needed to replace both parents in the next generation, accounting for some child mortality
One child replaces the mother, one replaces the father, and the extra 0.1 compensates for children who do not survive to reproductive age; at this TFR, a population's size would eventually stabilize absent migration. -
China's One-Child Policy, in effect from 1979 to 2015, produced which of the following unintended demographic consequences?
- A sharp increase in the total fertility rate
- A skewed sex ratio favoring males, due to cultural preference for sons
- A rapid rise in the crude birth rate
- An immediate reversal of the country's aging population trend
Show the answer
Answer. A skewed sex ratio favoring males, due to cultural preference for sons
Cultural preference for male heirs combined with the one-child limit led to sex-selective practices, producing a sex ratio imbalance with significantly more males than females in younger cohorts. -
What is chain migration, and give an example of the pattern it produces.
Show the answer
Answer. Migration in which people follow relatives or community members to a specific destination, often producing ethnic enclaves such as Little Italy or Chinatown neighborhoods in a city
Once one family member establishes themselves abroad, they provide information, housing, and support that draws additional relatives and community members to the same destination, reinforcing a concentrated migrant community there. -
How does a refugee differ from an internally displaced person (IDP)?
Show the answer
Answer. A refugee has crossed an international border fleeing persecution or conflict, while an IDP has been forced to flee but remains within their home country's borders
Both are forms of forced migration, but the refugee's crossing of a national border is the key legal distinction, since it determines eligibility for international refugee protections that do not apply to IDPs. -
Explain why a country with a total fertility rate at or below replacement level can still experience population growth for several decades.
Show the answer
Answer. Because population momentum from a previously large, youthful cohort continues to produce births as those people reach reproductive age, even after fertility per woman has fallen
A large existing cohort of young people will still have children even at a lower TFR, so total births continue to exceed deaths for a generation or more before growth actually levels off. -
Which stage of the epidemiological transition model corresponds to DTM Stage 3, when death rates are low and causes of death shift toward chronic conditions?
- The stage of pestilence and famine
- The stage of receding pandemics
- The stage of degenerative and human-created diseases
- The stage of the resurgence of infectious diseases
Show the answer
Answer. The stage of degenerative and human-created diseases
As sanitation and medicine improve and death rates stay low into DTM Stage 3–4, leading causes of death shift from infectious disease to chronic and degenerative conditions such as heart disease and cancer, matching the third epidemiological transition stage. -
A migrant from a rural village wants to move to a distant capital city for work, but a nearby regional city offers similar job opportunities at much lower cost. What concept explains why the migrant may settle in the regional city instead?
- Intervening obstacle
- Intervening opportunity
- Distance decay
- Chain migration
Show the answer
Answer. Intervening opportunity
An intervening opportunity is a closer, adequate alternative destination that satisfies the migrant's needs, reducing the likelihood they will travel farther to their originally intended destination. -
What is a key economic effect of emigration on a migrant's country of origin?
Show the answer
Answer. An inflow of remittances sent home by emigrants, alongside the risk of brain drain if skilled workers leave
Remittances can become a major source of national income and reduce poverty, but if the emigrants are highly educated or skilled, the origin country also loses valuable human capital, a tradeoff known as brain drain.
What people get wrong
- Confusing arithmetic density with physiological density. Arithmetic density divides population by total land area; physiological density divides population by arable land only, and is the better measure of pressure on food-producing land — always check which denominator a question specifies.
- Assuming Stage 4 or 5 countries have zero or negative population growth right now. A country can be in Stage 4 with low fertility but still growing in raw numbers due to population momentum from a previous youthful age structure — don't equate 'low NIR' with 'shrinking population.'
- Mixing up push and pull factors on free-response questions. A push factor is a negative condition at the origin (e.g., 'lack of jobs at home'); the same idea phrased as a positive draw at the destination (e.g., 'more jobs available') is a pull factor — restate the factor from the migrant's point of origin or destination before labeling it.
- Treating total fertility rate of 2.1 as an instant stop to population growth. Replacement-level fertility only stabilizes population size in the long run after population momentum from existing young cohorts works its way through — a country can hit TFR 2.1 and still grow for decades.
- Reading a population pyramid shape and assuming a DTM stage without checking birth and death rate data if it's given. Pyramid shape is a consequence of CBR/CDR/TFR, not an independent fact — use whichever data the question actually provides, and use both together when both are given.
- Assuming all population policies are anti-natalist. Some governments (e.g., France, Hungary, historically Romania) adopt pro-natalist policies to raise birth rates — read the policy's goal (raise vs. lower growth) before assuming its effect on composition.
Drill this unit until it sticks
These questions come back on a schedule built from what you get wrong, alongside the rest of AP Human Geography. Free, and no account needed to start.