Since independence, Botswana has had the highest average economic growth rate in the world, averaging about 9% per year from 1966 to 1999. Growth in private sector employment has averaged about 10% per annum over the first 30 years of independence. The government has consistently maintained budget surpluses and has extensive foreign exchange reserves. Botswana's impressive economic record has been built on a foundation of diamond mining, prudent fiscal policies, international financial and technical assistance, and a cautious foreign policy. It is rated the least corrupt country in Africa, according to international corruption watchdog,