Hungry for yield in a low yield environment mutual funds and others have bought up large positions in Puerto Rican bonds yielding around 8-10%. Until recently no one would touch the damn things with good reason: it's a hopelessly corrupt overcrowded island (3.7 million people crammed into 8,870 km2) with an economy that's been stagnant for decades and an ambiguous post-colonial status of 'Estado Libre Asociado' whatever that means.
All that aside it hasn't stopped them or the big banks assisting them from issuing 52-70 billion in municipal debt securities. No ones even sure of the valuation it's so shaky.
A chain is only as strong as it's weakest link and if Puerto Rico were the 51st State that some consider it, it would indeed be the weakest link fiscally speaking or among the weakest with California, Illinois, and some others. It's already the poorest with median household income of $18,314 for 2009 compared to the poorest state in the Union, Mississippi with a median household income of $36,646 in 2009. http://www.economist.com/news/finance-and-economics/21588364-heavily-indebted-island-weighs-americas-municipal-bond-market-puerto-pobrehttp://www.forbes.com/sites/jakezamansky/2013/11/19/a-puerto-rico-bond-investors-portfolio-gets-scarier-with-potential-downgrade-to-junk/http://www.marketwatch.com/story/puerto-rico-muni-bonds-get-some-tailwind-2013-11-01http://www.cnbc.com/id/101172850