NEW YORK--(BUSINESS WIRE)--Puerto Rico's longstanding and deepening fiscal challenges led most closed-end municipal bond funds (CEF) to reduce holdings of the debt of the commonwealth, protecting the majority of these funds from substantial negative effects, says Fitch Ratings. Of 192 Fitch-rated closed-end muni funds, 57 still had some Puerto Rico holdings. Of the group with exposure to Puerto Rico, the majority had less than 2% holdings, with an average of about 1.1% as of the end of May 2015