Population and Demography
Population data
Demography studies population size, structure, distribution and change. Change equals natural increase (births minus deaths) plus net migration. Rates (birth rate, death rate, natural growth) are expressed per 1,000 people, so they are comparable across countries of different size. The demographic transition model describes stages from high birth and death rates to low ones, with a transitional population explosion.
Structure and distribution
Population pyramids reveal age and sex structure: broad bases mean young, fast-growing populations; narrow bases mean ageing populations. Dependency ratios compare non-working to working-age people. Density is people per unit area, but it can mislead because populations cluster in cities and fertile lowlands. Push and pull factors explain migration; refugees and economic migrants differ in cause.
Traps
Do not confuse natural increase with total growth (migration matters); do not read a rate as an absolute number; and remember that a declining birth rate can still mean a growing population because of momentum.
Worked example
A country has a birth rate of 12, a death rate of 10 and net migration of +3 per 1,000. Growth is 12 − 10 + 3 = 5 per 1,000, or 0.5%. If its population is 10 million, that is 50,000 people per year.