Human development index? HDI explain?

HDI is a tool that the UN created to measure how 'developed' a country is based on 4 factors. These are; life expectancy, expected years of schooling, GNI (gross national income) per capita (person) and mean years of schooling. HDI is also a much more accurate tool for calculating development (as opposed to GDP) as it includes social factors, whereas GDP only includes economic factors.