Puerto Ricans, as U.S. citizens, are able to travel freely between Puerto Rico and the U.S. mainland. In the wake of Hurricane Maria, many of them sought refuge in Florida, New York and other parts of the U.S. Using anonymized cell phone location data for some 500,000 smart phones, data analysis firm Teralytics was able to map where Puerto Ricans moved from August 2017 to February 2018. CityLab has the maps and the story: “Between these months, nearly 6 percent of the Puerto Rican population left the island and is still living in the continental U.S. Another 6 percent left between October and September 2017 but returned to the island by February 2018.”