Libya(56) has the highest rating for an African nation on the Human Development Index and is the only African nation ranked in the "High" category. Next would be Tunisia(91), Algeria(104), Egypt (112) and Sudan (178) These exclude the island nations of Seychelles(50) and Mauritius(65). The Human Development Index (HDI) is a comparative measure of life expectancy, literacy, education, and standards of living for countries worldwide. It is a standard means of measuring well-being, especially child welfare. It is used to distinguish whether the country is a developed, a developing, or an under-developed country, and also to measure the impact of economic policies on quality of life.