Nearly one-sixth of the United States territory of Puerto Rico is planted with sugar cane. A major part of the island's economy, the cane is refined into sugar, molasses, rum, and other products at five huge centrales, or sugar mills. Most cane plantations are situated on the coastal lowlands, where they benefit from the stable tropical climate and abundant rainfall. To shield its economy from fluctuations in the world sugar market, the Puerto Rican government encourages planting of new crops such as coffee, pineapple, citrus fruit, and other commodities that cannot be grown elsewhere in the United States.