The Human Development Index (HDI) is a statistic composite index of life expectancy, education, and per capita income indicators, which are used to rank countries into four tiers of human development. A country scores a higher HDI when the lifespan is higher, the education level is higher, and the GNI (PPP) per capita is higher. It was developed by Indian Nobel prize winner Amartya Sen and Pakistani economist Mahbub ul Haq, with help from Gustav Ranis of Yale University and Lord Meghnad Desai of the London School of Economics, and was further used to measure a country's development by the United Nations Development Program (UNDP)'s Human Development Report Office.
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)". The index does not take into account several factors, such as the net wealth per capita or the relative quality of goods in a country. This situation tends to lower the ranking for some of the most advanced countries, such as the G7 members and others.
The index is based on the human development approach, developed by ul Haq, often framed in terms of whether people are able to "be" and "do" desirable things in life. Examples include—Being: well fed, sheltered, healthy; Doings: work, education, voting, participating in community life. The freedom of choice is central—someone choosing to be hungry (as during a religious fast) is quite different from someone who is hungry because they cannot afford to buy food, or because the country is in a famine.