<Table> <Tr> <Td> 1.000--0.800 (very high) 0.700--0.799 (high) 0.555--0.699 (medium) </Td> <Td> 0.350--0.554 (low) Data unavailable </Td> </Tr> </Table> <Tr> <Td> 1.000--0.800 (very high) 0.700--0.799 (high) 0.555--0.699 (medium) </Td> <Td> 0.350--0.554 (low) Data unavailable </Td> </Tr> <P> 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 GDP 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 the country's development by the United Nations Development Program (UNDP). </P> <P> 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 . </P>

The united nations measures the average income in countries through a complex index called