Uganda has substantial natural resources, including fertile soils, regular rainfall, small deposits of copper, gold, and other minerals, and recently discovered oil. Uganda has never conducted a national minerals survey. Agriculture is the most important sector of the economy, employing over 80% of the work force. Coffee accounts for the bulk of export revenues. Since 1986, the government - with the support of foreign countries and international agencies - has acted to rehabilitate and stabilize the economy by undertaking currency reform, raising producer prices on export crops, increasing prices of petroleum products, and improving civil service wages. The policy changes are especially aimed at dampening inflation and boosting production and export earnings. Since 1990 economic reforms ushered in an era of solid economic growth based on continued investment in infrastructure, improved incentives for production and exports, lower inflation, better domestic security, and the return of exiled Indian-Ugandan entrepreneurs. Uganda has received about $2 billion in multilateral and bilateral debt relief. In 2007 Uganda received $10 million for a Millennium Challenge Account Threshold Program. The global economic downturn has hurt Uganda's exports; however, Uganda's GDP growth is still relatively strong due to past reforms and sound management of the downturn. Oil revenues and taxes will become a larger source of government funding as oil comes on line in the next few years. Instability in southern Sudan is the biggest risk for the Ugandan economy in 2011 because Uganda's main export partner is Sudan, and Uganda is a key destination for Sudanese refugees.