Human populations practice questions.

An age–sex pyramid with a very wide base and steeply narrowing sides indicates a population with

• a high birth rate and rapid growth potential
• a low birth rate and an ageing structure
• balanced birth and death rates over time
• heavy immigration of working-age adults

Answer: a high birth rate and rapid growth potential

A wide base means each new cohort is larger than the one before it, which only happens when the birth rate is high; the steep narrowing shows significant mortality in each age class. An ageing population produces the opposite shape — a narrow base and a bulging top.

A government makes contraception free, raises the legal age of marriage and runs campaigns promoting smaller families. This set of measures is best described as

• a pro-natalist policy, aiming to raise fertility
• an anti-natalist policy, aiming to lower fertility
• a migration policy, aiming to change net inflows
• a public health policy, aiming to lower mortality

Answer: an anti-natalist policy, aiming to lower fertility

Every measure targets the number of births, and all push in the same downward direction — that is anti-natalist. Pro-natalist packages use the same policy levers (money, law, campaigns) but reversed, which is why the direction, not the instrument, defines the label.

A high-income country can record a higher crude death rate than a much poorer country mainly because

• its health system records deaths more completely
• its birth rate is too low to offset the deaths
• its population contains a larger share of elderly people
• crude death rates always rise with income levels

Answer: its population contains a larger share of elderly people

The crude death rate divides deaths by the whole population without adjusting for age, so a country full of octogenarians records many deaths per 1000 however good its hospitals are. This is why crude rates are a poor development indicator on their own.

As fertility falls, the share of working-age adults in a country rises sharply for a few decades. The potential economic benefit this creates is known as

• population momentum
• the epidemiological transition
• replacement-level fertility
• the demographic dividend

Answer: the demographic dividend

With fewer children to support and elderly cohorts still small, a large share of the population can work and save — the demographic dividend. It is a window, not a permanent state: the same bulge generation eventually retires and the dependency burden returns.

In a class test a student writes: 'A country in stage 2 of the demographic transition model has the lowest natural increase rate of the five stages, because its death rate is falling.' Identify the error in this statement.

• Falling death rates while birth rates stay high give stage 2 the highest natural increase rate of the five stages.
• Death rates do not fall in stage 2 at all; they begin to fall only once a country has reached stage 4 and health care is widely available.
• Stage 2 has the lowest natural increase rate only in the special case where net emigration from the country is also taken into account.
• Birth rates in stage 2 fall faster than death rates, so the natural increase rate there is negative.

Answer: Falling death rates while birth rates stay high give stage 2 the highest natural increase rate of the five stages.

Stage 2 is the stage of maximum natural increase: sanitation, food supply and medicine have already pushed the crude death rate down while the crude birth rate is still high. Reading stage 2 as the slowest-growing stage is one of the most common misreadings of the model.

From the early 1990s several countries in southern Africa recorded a rising crude death rate at the same time as their crude birth rate was falling. Identify the feature of the demographic transition model that this sequence does not fit.

• The model assumes that the crude birth rate falls before the crude death rate begins to fall.
• The model treats the crude death rate as falling and then staying low once a country has left stage 1.
• The model applies only to countries whose total population is growing, and it makes no statement at all about countries that are losing population.
• The model measures fertility with the total fertility rate rather than with the crude birth rate.

Answer: The model treats the crude death rate as falling and then staying low once a country has left stage 1.

In the model mortality falls first and then remains low; the adult mortality of the HIV/AIDS epidemic reversed that trend for two decades. The model is a description of European industrialisation, not a law, so a country can leave its sequence without the country being anomalous.