The Human Development Index (HDI) is a composite statistic of life expectancy, education, and per capita income indicators, which are used to rank countries into four tiers of human development. A country scores higher HDI when the lifespan is higher, the education level is higher, the GDP per capita is higher, the fertility rate is lower, and the inflation rate is lower. The HDI was developed by the Pakistani economist Mahbub ul Haq working alongside Indian economist Amartya Sen, often framed in terms of whether people are able to "be" and "do" desirable things in their life, and was published by the United Nations Development Programme.