Free MCAT-style practice, 9B
MCAT Demographic Transition and Population Growth Practice Questions
Nine free MCAT-style practice questions on growth rate, doubling time, dependency ratios, the demographic transition, population pyramids, Malthus and push and pull migration, with full explanations.
Quick concept primer
Population change equals births minus deaths plus immigrants minus emigrants. Crude birth and death rates are expressed per 1,000 people, so a growth rate of 10 per 1,000 is 1 percent per year. The rule of 70 estimates doubling time: 70 divided by the percent growth rate. The total dependency ratio compares people under 15 and 65 and over with those aged 15 to 64, times 100. A total fertility rate of about 2.1 is replacement level in low-mortality populations.
The demographic transition model describes death rates falling first (sanitation, nutrition, medicine) while birth rates stay high, producing rapid growth in stage 2. Birth rates then fall with urbanization, women's education and contraception (stage 3) until both are low (stage 4). Population pyramids record this history: a wide base signals high fertility, near-vertical sides signal stability, and a narrow base with a heavy top signals aging. Malthus argued population grows geometrically while food grows arithmetically, held in check by positive checks (raising deaths) and preventive checks (lowering births). Migration reflects push factors at the origin and pull factors at the destination.
Traps: subtract emigrants, and remember that growth can continue after fertility reaches replacement because of population momentum.
9 practice questions
Question 1
In one year, a town of 80,000 people records 1,200 births, 560 deaths, 400 immigrants and 240 emigrants. What is the town's annual growth rate?
- 0.8 percent
- 1.0 percent
- 1.3 percent
- 2.0 percent
Show answer and explanation
Answer: B. 1.0 percent
Net change is 1,200 minus 560 plus 400 minus 240, which equals 800. Dividing 800 by 80,000 gives 0.010, or 1.0 percent (natural increase of 8 per 1,000 plus net migration of 2 per 1,000). 0.8 percent ignores migration, and 1.3 percent comes from forgetting to subtract the 240 emigrants.
Question 2
A country's population is growing at a steady 1.4 percent per year. Using the rule of 70, about how long will it take the population to double?
- 14 years
- 35 years
- 50 years
- 98 years
Show answer and explanation
Answer: C. 50 years
The rule of 70 estimates doubling time as 70 divided by the percent annual growth rate: 70 divided by 1.4 equals 50 years. 35 years would correspond to 2 percent growth, and 98 years comes from multiplying 70 by 1.4 instead of dividing.
Question 3
A region has 18,000 residents under age 15, 60,000 residents aged 15 to 64 and 12,000 residents aged 65 and older. What is its total dependency ratio?
- 20
- 30
- 33
- 50
Show answer and explanation
Answer: D. 50
The total dependency ratio is (people under 15 plus people 65 and over) divided by people aged 15 to 64, times 100: 30,000 divided by 60,000 times 100 equals 50. The old-age ratio alone is 20 and the youth ratio alone is 30. 33 results from wrongly dividing by the total population of 90,000.
Question 4
Researchers compile vital rates for one country.
| Year | Crude birth rate (per 1,000) | Crude death rate (per 1,000) |
|---|---|---|
| 1950 | 44 | 28 |
| 1970 | 43 | 15 |
| 1990 | 41 | 10 |
Which stage of the demographic transition model best describes this country during this period?
- Stage 1
- Stage 2
- Stage 3
- Stage 4
Show answer and explanation
Answer: B. Stage 2
Birth rates stay high while death rates fall steeply, so natural increase rises from 16 to 31 per 1,000 (1.6 to 3.1 percent per year). Rapid growth from falling mortality with persistently high fertility defines stage 2. Stage 1 has high birth and death rates, stage 3 has falling birth rates, and stage 4 has both rates low.
Question 5
A population pyramid has a narrow base, its widest bars in the 50 to 69 age range, and noticeably more women than men in the oldest age groups. Which description best fits this population?
- Constrictive, with below-replacement fertility and population aging
- Expanding, with high fertility and a young population
- Stationary, with replacement fertility for many decades
- Expanding, with a recent rise in births
Show answer and explanation
Answer: A. Constrictive, with below-replacement fertility and population aging
A base narrower than the middle shows that recent birth cohorts are smaller than earlier ones, the signature of below-replacement fertility, and a heavy top reflects aging. Women outnumber men at old ages because of longer female life expectancy. Expanding pyramids have wide bases, and a stationary pyramid has nearly vertical sides.
Question 6
During a series of poor harvests, families in a farming region respond by delaying marriage and having fewer children. In Malthus's framework, this response is an example of:
- a positive check.
- a preventive check.
- a demographic dividend.
- population momentum.
Show answer and explanation
Answer: B. a preventive check.
Malthus called influences that reduce births, such as delayed marriage and moral restraint, preventive checks. Positive checks raise mortality through famine, disease or war. The demographic dividend is an economic boost from a large working-age share, and population momentum is continued growth driven by a young age structure.
Question 7
Researchers interview nurses who left Country X to work in Country Y. Each of the following would be classified as a pull factor EXCEPT:
- higher nursing wages in Country Y.
- relatives already living in Country Y.
- civil conflict in Country X.
- open nursing positions in Country Y.
Show answer and explanation
Answer: C. civil conflict in Country X.
In Lee's push-pull framework, pull factors attract migrants to the destination, while push factors drive them away from the origin. Civil conflict in the home country is a push factor. Higher wages, family networks and available jobs in the destination all pull migrants toward Country Y.
Question 8
A country's total fertility rate falls to about 2.1, the replacement level, yet its population keeps growing for several more decades with no immigration. What is the best explanation?
- A large share of the population is young, so many people are still entering their childbearing years.
- Death rates are rising faster than birth rates.
- Positive checks are increasing the number of births.
- Emigration exceeds immigration.
Show answer and explanation
Answer: A. A large share of the population is young, so many people are still entering their childbearing years.
Population momentum occurs when earlier high fertility leaves a young age structure. Even if each woman averages about two children, the large number of women in reproductive ages produces more births than deaths for decades. Rising death rates or net emigration would slow growth, and positive checks increase deaths, not births.
Question 9
A country with no migration has had a total fertility rate of about 1.4 for 25 years, and life expectancy is high. If these rates continue, which long-run outcome is most likely?
- Rapid growth with a widening pyramid base
- A stable population size with a rectangular pyramid
- Growth driven mainly by rising fertility
- Eventual population decline with a rising old-age dependency ratio
Show answer and explanation
Answer: D. Eventual population decline with a rising old-age dependency ratio
A total fertility rate well below replacement means each generation is smaller than the one before, so once momentum is exhausted the population shrinks. Smaller young cohorts and long lives raise the share of older people relative to working-age adults, increasing the old-age dependency ratio. Growth or a stable rectangle would require fertility near or above replacement.