All but one county in Puerto Rico lost population during 2010 to 2015, further entrenching population declines that began at lower levels at the start of the century.
According to a Pew Research Center analysis of newly released county-level Census Bureau data, Gurabo, located in eastern Puerto Rico, was the only county, or "municipio," that saw a population increase.
The county with the largest decrease was San Juan, where the island's capital and largest metro area are located. There, the population fell by 40,000 people to 355,000. Nine other counties saw their populations decline by at least 10 percent during those years.
Pew said that population increase had been the norm in Puerto Rico until 2,000, when a 10-year drop of about 2.8 percent began. But that accelerated in 2010.
The population fell to 3.47 million in 2015, down 334,000 from 2000. Three quarters of that drop has occurred since 2010.
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Puerto Rico is going through a severe financial crisis. Thousands of its residents have been leaving the island in the last several years and coming to the U.S. mainland to seek better job opportunities.
The Census Bureau estimates that the Puerto Rico population will decrease to 2.98 million by 2050.