The acronym "HDI" stands for the Human Development Index. This index is used to measure whether a particular country is underdeveloped, developing or fully developed. The index relies on levels of education, life expectancy, literacy and gross domestic product to rank countries into groups.
The HDI has been used since 1975 by the United Nations, and is included in the Human Development Report. Early calculations were heavily weighted toward income per capita, however, later calculations considered the overall quality of living. In 2013, the countries with the highest HDI rating included Norway, Australia, the United States, the Netherlands and Germany.