The Human Development Index (HDI) is a comparative measure of life expectancy, literacy, education and standards of living for countries worldwide that is used to distinguish whether a country is a developed, a developing or an under-developed country. The HDI is a standard means of measuring well-being, especially child welfare. The HDI is also used to measure the impact of economic policies on quality of life. The index was developed in 1990 by Pakistani economist Mahbub ul Haq and Indian economist Amartya Sen.
Under the two main categories of Developed and Developing Countries, there are four broad categories* based on HDI:
 Very high human development (added in the report for 2007),
 High human development
 Medium human development
 Low human development.
* Starting in the report for 2007, the first category was referred to as developed countries, and the last three are all grouped in developing countries (split in the same report).
Wikipedia: List of Countries by Human Development Index