Test your Population Knowledge

Total fertility rate is a period measure. It describes the average number of live births a hypothetical woman would have if she experienced the age-specific fertility rates of that period throughout her reproductive life, without being subject to mortality. It is not the observed completed family size of women alive today. Sources: UN World Population Prospects 2024 methodology (PDF).

Purchasing power parities account for differences in price levels, helping convert currencies into a comparable unit. Monetary poverty comparisons also need a clearly labelled threshold and price basis. The World Bank cautions that a country’s national poverty line is more appropriate for assessing poverty in that country; an international line does not capture every dimension of poverty. Sources: World Bank: international poverty comparisons.

IPBES identifies five major direct drivers: land- and sea-use change, direct exploitation of organisms, climate change, pollution and invasive alien species. These interact with underlying economic and social drivers, including production, consumption, trade, governance and demographic trends. Responsibility is unequal: high-income countries have much higher material use per person than low-income countries. Demographic trends alone do not explain environmental harm. Sources: IPBES Global Assessment summary (PDF); UNEP: Global Resources Outlook 2024.

Population ageing describes a change in age structure towards a greater concentration of people at older ages. It is a demographic description, not a judgement about anyone’s value. Changes in age structure have implications for healthcare, social protection, households and labour markets, and should inform planning. Sources: UN: population ageing.

The 2024 medium scenario projects approximately 10.2 billion people in 2100. This is a modelled future based on assumptions, not a guaranteed outcome or a population target. Different scenarios and methods can produce different results. Sources: UN World Population Prospects 2024 workbook (Excel); UN World Population Prospects 2024 summary (PDF).

Reproductive rights and bodily autonomy are ends in themselves. People should have access to voluntary family planning, healthcare and education, and be able to realise their own reproductive intentions. Governments should remove barriers to choice rather than pressure people to have more or fewer children. Sources: UNFPA: State of World Population 2025.

Reproductive rights are ends in themselves. IPBES identifies demographic trends, production, consumption, trade and governance among the underlying drivers of change in nature. Population dynamics can interact with resource demand, alongside infrastructure, technology and policy. UNEP’s 2024 Global Resources Outlook highlights much higher material use per person in high-income countries than in low-income countries. Population numbers alone do not explain environmental harm, and people’s reproductive choices are not environmental targets. Sources: IPBES Global Assessment summary (PDF); UNEP: Global Resources Outlook 2024.

The percentage growth rate and the increase in numbers are different measures. For example, 1% of 10 million is 100,000, while 0.75% of 20 million is 150,000. A larger starting population can therefore have a larger increase even at a lower percentage rate. These are illustrative calculations, not estimates for a country or historical year.