The Human Development Index (HDI) is a composite measure of life expectancy, education, and income that ranks countries based on human development. Established by Mahbub ul Haq and utilized by the UNDP, the HDI has evolved to include the Inequality-adjusted Human Development Index (IHDI) that accounts for inequality in measurements. The annual Human Development Reports, starting from 1990, provide insights into human development themes and continue to influence global development discussions.