Puerto Rico has one of the most dynamic economies in the Caribbean region. Plantation sugar production dominated Puerto Rico's economy until the 1940s. Industry has surpassed agriculture as the primary sector of economic activity and income. Encouraged by duty free access to the U.S. and by tax incentives, U.S. firms have invested heavily in Puerto Rico since the 1950s (U.S. minimum wage laws apply). As a result, Puerto Rico's export and import has prospered, nearly doubled between fiscal years 1987 and 1997.