Changing populations and places practice questions.

On a map of internal migration each city is drawn as a proportional circle whose area represents the number of arrivals it received in one year. One city received four times as many arrivals as another. How do the radii of the two circles compare?

• The radius is sixteen times as large
• The radius is four times as large
• The radius is twice as large
• The radius is unchanged, only the shading differs

Answer: The radius is twice as large

Area varies with the square of the radius, so a fourfold value needs the radius multiplied by the square root of four. Scaling the radius directly by the value is the standard error and makes the largest destination look far more dominant than the migration data warrant.

Tens of millions of workers from rural provinces such as Sichuan have moved to work in coastal manufacturing cities such as Shenzhen, China, returning home mainly for the spring festival. Which type of migration is this?

• International economic labour migration
• Voluntary internal rural-urban migration
• Forced internal displacement
• International refugee movement

Answer: Voluntary internal rural-urban migration

The movement stays inside China's borders and is chosen for economic reasons, making it voluntary internal rural-urban migration — the largest migration flow in the world. The typical error is calling any large labour flow 'international', or any hardship-driven move 'forced'.

A population pyramid drawn for a single university town has a pronounced bulge at ages 18-24 that is absent from the national pyramid for the same year. What does this contrast show?

• The town must be at an earlier stage of the demographic transition.
• The town's total fertility rate must be above the national figure.
• Age structure at the local scale can differ sharply from the national scale.
• The national pyramid must have been drawn for a different year.

Answer: Age structure at the local scale can differ sharply from the national scale.

A pyramid describes whoever is present, so short-term migration for study can dominate a local profile without any difference in births or deaths. Reading a national explanation onto a local pyramid is the standard error with this resource.

Nurses and doctors trained in a middle-income country emigrate to work in high-income countries. Which consequence for the country they leave follows most directly?

• Its population density falls sharply in the areas they leave.
• Its health services lose staff whose training the country paid for.
• Its crude birth rate rises in the year the migrants depart.
• Its dependency ratio falls because young adults have left.

Answer: Its health services lose staff whose training the country paid for.

The loss is of public investment as well as of labour: the state met the cost of training and another country receives the benefit. Losing young adults raises the dependency ratio rather than lowering it, because they were part of the working-age denominator.

The town of Ashford Vale has 5 600 residents aged 0-14, 20 000 aged 15-64 and 3 400 aged 65 and over. Calculate the total dependency ratio (to the nearest whole number, per 100 people of working age). Answer: ___

Answer: 45

Total dependency ratio = ((0-14) + (65+)) / (15-64) x 100 = (5 600 + 3 400) / 20 000 x 100 = 45, so every 100 workers support 45 dependants. Adding the 65+ group to the working population instead of to the dependants is the standard slip.

The rural district of Bramfield covers 1 350 km² and is home to 48 600 residents. Calculate its population density (to the nearest whole number, in people km⁻²). Answer: ___

Answer: 36

Density = population / area = 48 600 / 1 350 = 36 people km⁻². Arithmetic density like this conceals internal clustering, which is why geographers also quote physiological density against cultivable land.