The Saudi Arabian economy is fueled almost entirely by the production and distribution of petroleum and its derivative products. It possesses more than 20% of the world's proven petroleum reserves, ranks as the largest exporter of petroleum, and plays a leading role in OPEC. The petroleum sector accounts for roughly 80% of budget revenues, 45% of GDP, and 90% of export earnings. About 40% of GDP comes from the private sector. Economic reforms proceed cautiously because of deep-rooted political and social conservatism. Saudi Arabia imports machinery and equipment, foodstuffs, chemicals, motor vehicles and textiles. Its main trading partners are the USA, Western Europe and Japan.