The chief occupations, which employ more than 60% of the workforce, are small-scale subsistence farming (producing rice, corn, root crops, citrus fruit, barley, wheat, and potatoes) and the raising of yaks, cattle, sheep, pigs, and tanguns, a sturdy breed of pony valued in mountain transportation. Wood and leather products, processed foods, alcoholic beverages, calcium carbide, textiles, and handicrafts are also important. Hydroelectric power is a most important resource, with some electricity being exported to India; it is the country's most important export. Fuels, grain, aircraft, machinery, vehicles, and fabrics are the major imports; cardamom and other spices, gypsum, timber, handicrafts, fruit, and precious stones are the other primary exports. Tourism is a significant though restricted activity, and it is the country's largest source of foreign exchange. Bhutan's economy is closely tied to that of India, both through trade and monetary links.