Mongolia's economy is centered on agriculture and mining. Economic activity in Mongolia has traditionally been based on herding and agriculture. Mongolia has rich mineral resources, and copper, coal, molybdenum, tin, tungsten, and gold account for a large part of industrial production. China is Mongolia's chief export partner and a main source of the "shadow" or "grey" economy. Remittances from Mongolians working abroad both legally and illegally constitute a sizeable portion.