The Human Development Index (HDI) is a summary measure of average achievement in key dimensions of human development: a long and healthy life, being knowledgeable and have a decent standard of living.

The HDI combined three dimensions (prior to 2010)

• Life expectancy at birth, as an index of population health and longevity to HDI
• Knowledge and education, as measured by the adult literacy rate (with two-thirds weighting) and the combined primary, secondary, and tertiary gross enrollment ratio (with one-third weighting).
• Standard of living, as indicated by the natural logarithm of gross domestic product per capita at purchasing power parity.

New method (2010 Index onwards)

• A long and healthy life: Life expectancy at birth
• Education index: Mean years of schooling and Expected years of schooling
• A decent standard of living: GNI per capita (PPP international dollars)
• In its 2010 Human Development Report, the UNDP began using a new method of calculating the HDI.

Inequality Adjusted Human Development Index(IHDI)

The 2010 Human Development Report introduced an Inequality-adjusted Human Development Index (IHDI). While the simple HDI remains useful, it stated that “the IHDI is the actual level of human development (accounting for inequality)”, and “the HDI can be viewed as an index of ‘potential’ human development (or the maximum IHDI that could be achieved if there were no inequality)”.