Salt and opium were the subject of lucrative government monopolies from VOC times. To begin with, they were ‘farmed' that is, the right to distribute opium or salt within a district was given to a farmer (pachter) in exchange for substantial payment. In the 18th century opium was distributed to farm (pacht) holders who enjoyed a monopoly of distribution within their regions. In 1815, salt sales were transferred to an official agency, the Zoutregie, though they remained a valuable source of revenue. The opium monopoly did not come under an Opiumregie until 1894, after a public campaign in the Netherlands against the trade.
Butcher, John, and Howard Dick, eds, The Rise and fall of revenue farming : business elites and the emergence of the modern state in Southeast Asia. New York: St. Martin's Press, 1993.
Rush, James, R. Opium to Java: Revenue Farming and Chinese Enterprise in Colonial Indonesia, 1860-1910. Ithaca NY: Cornell University Press, 1990.