What it means: the UN's summary measure of a country's development, combining life expectancy, years of schooling and income per person. The fainter line adjusts it for how unequally health, education and income are shared; the gap between the two lines is the loss from inequality. It is compiled by the UN Development Programme, an international body, rather than a UK statistics office, and the latest figures are for 2023. The method is revised each year and past years are recalculated, so use the chart rather than older reports to compare years. A change of 0.003 or more counts.

Source: UN Development Programme, Human Development Report 2025, composite indices time series.