Human Development Index (HDI)

The Human Development Index (HDI) is a composite statistic published by the United Nations Development Programme that summarizes a country's average achievement across three dimensions: health, measured by life expectancy at birth; education, measured by years of schooling; and standard of living, measured by gross national income per capita. Each country receives a score between 0 and 1, with values closer to 1 indicating higher development.

The index is built by normalizing each dimension to a 0-1 scale against fixed minimum and maximum values, then combining the three normalized scores using a geometric mean rather than a simple average. The geometric mean penalizes countries that do poorly on one dimension even if they do well on others, so a high income score cannot fully offset a low education or health score. This differs from the gini coefficient, which measures inequality within a country rather than its overall level of development.

HDI is widely used to compare development across countries and over time, alongside indicators like the poverty headcount ratio and progress toward the Sustainable Development Goal (SDG) indicators. Its main limitation is that a single national average can mask large internal disparities; a country with wide income inequality can post the same HDI as a more equal one, which is why UNDP also publishes an inequality-adjusted version and why analysts pair HDI with measures like median household income or the Gini coefficient rather than reading it alone.