How is the Human Development Index (HDI) calculated?

The Human Development Index (HDI) is calculated by averaging three key dimensions: life expectancy, education, and income indices.

The HDI, developed by the United Nations Development Programme (UNDP), is a composite statistic that aims to rank countries based on their human development. It is a summary measure for assessing long-term progress in three basic dimensions of human development: a long and healthy life, access to knowledge, and a decent standard of living.

The first dimension, a long and healthy life, is measured by life expectancy at birth. This data is collected from life tables and reflects the ability of a nation to provide adequate healthcare facilities to its citizens. The higher the life expectancy, the better a country's HDI ranking.

The second dimension, access to knowledge, is measured by mean years of schooling for adults aged 25 years and more and expected years of schooling for children of school entering age. Mean years of schooling is an estimation of the average number of years of education received by people ages 25 and older in their lifetime based on education attainment levels of the population converted into years of schooling based on theoretical duration of each level of education attended. Expected years of schooling is a calculation of the total number of years of schooling a child of school-entry age can expect to receive over their lifetime, assuming that the probability of his or her being enrolled in school at any particular future age is equal to the current enrolment ratio at that age.

The third dimension, a decent standard of living, is measured by Gross National Income (GNI) per capita expressed in terms of Purchasing Power Parity (PPP) dollars. This reflects the average income of a country's citizens. Countries with higher GNI per capita will have a better HDI ranking.

These three indices are then averaged to yield the HDI. Each dimension is given equal weight in the calculation. The HDI ranges from 0 to 1, with 1 being the highest possible score. Countries are then ranked based on their HDI score, providing a comparative measure of development and quality of life.