The island’s troubles have their origin in an era of corporate tax incentives in the 1970s that exempted firms from paying federal taxes on profits earned in Puerto Rico. This was done to prevent tax-allergic American companies from setting up shop outside the country. Pharmaceutical, textile and electronics companies flocked to the island to spark a manufacturing boom that lasted for around two decades. In 1996, the American government, under the Clinton administration, started weaning Puerto Rico off these tax breaks to offset some of the country’s federal deficit. The largesse disappeared entirely in 2006 and its economy has suffered...