Botswana has maintained one of the world's highest growth rates since independence in 1966. Through fiscal discipline and sound management, Botswana has transformed itself from one of the poorest countries in the world to a middle-income country with a per capita GDP of $8,800 in 2003. Two major investment services rank Botswana as the best credit risk in Africa. Diamond mining has fueled much of the expansion and currently accounts for more than one-third of GDP and for nine-tenths of export earnings. Tourism, subsistence farming, and cattle raising are other key sectors. On the downside, the government must deal with high rates of unemployment and poverty. Unemployment officially is 21%, but unofficial estimates place it closer to 40%. HIV/AIDS infection rates are the highest in the world and threaten Botswana's impressive economic gains. Long-term prospects are overshadowed by the expected leveling off in diamond mining production.