The French established an opium franchise to put their new colony on a paying basis only six months after they annexed Saigon in 1862. Opium was imported from India, taxed at 10 percent of value, and sold by licensed Chinese merchants to all comers. Opium became an extremely lucrative source of income, and this successful experiment was repeated as the French acquired other areas in Indochina. Shortly after the French established a protectorate over Cambodia (1863) and central Vietnam (1883), and annexed Tonkin (northern Vietnam, 1884) and Laos (1893), they founded autonomous opium monopolies to finance the heavy initial expenses of colonial rule. While the opium franchise had succeeded in putting southern Vietnam on a paying basis within several years, the rapid expansion of French holdings in the 1880s and 1890s created a huge fiscal deficit for Indochina as a whole. Governor-General Paul Doumer reorganized the opium business in 1899, expanding sales and sharply reducing expenses. After consolidating the five autonomous opium agencies into the single Opium Monopoly, Doumer constructed a modern, efficient opium refinery in Saigon to process raw Indian resin into prepared smoker's opium. The new factory devised a special mixture of prepared opium that burned quickly, thus encouraging the smoker to consume more opium than be might ordinarily. Under his direction, the Opium Monopoly made its first purchases of cheap opium from China's Yunnan Province so that government dens and retail shops could expand their clientele to include the poorer workers who could not afford the high-priced Indian brands. More dens and shops were opened to meet expanded consumer demand (in 1918 there were 1,512 dens and 3,098 retail shops).