uerto Rico's economic decline began before the Great Recession, in part due to the loss of a tax credit for companies that set up manufacturing on the island. Those credits expired in 2006.
Since then, the drop in employment continues to drive the out-migration as unemployment remains stubbornly high at 12.6 percent—more than twice the U.S. average rate of 5.3 percent, as of June.
The departure of younger workers has left the territory with an older, poorer population, further straining the government's social services. It's also left the local economy with fewer active workers; as of June, just 40 percent of Puerto Rico's population was officially counted as part of the labor force. (The U.S. state average in June was 62.6 percent.)
Some of those missing from the workforce are part of the local "informal" economy that employs "a large segment of the population" and allows "workers and firms to avoid many of the taxes and other costs associated with formal employment," according a report last year by the New York Federal Reserve. Because that work is conducted off the books, it's difficult to know just how much tax is lost, but the New York Fed report put the informal economy at roughly a quarter of Puerto Rico's gross domestic product.
With its job base shrinking, and sales and income taxes lost to an underground economy, the government has financed its budget shortfalls with borrowed money, adding to a crushing debt burden. As a share of GDP, Puerto Rico's $72 billion in debt has swollen its public borrowing from 60 percent of GDP in 2000 to more than 100 percent as of 2013, according to the New York Fed.
https://www.cnbc.com/2015/08/04/heres-why-puerto-ricos-broke.html