Two large bond rating agencies, Moody’s Investors Service (Moody’s) and Standard and Poor’s (S&P) provide annual default statistics for the municipal bonds that they rate. S&P reports that its rated municipal bonds defaulted only 47 times from 1986 to 2011. Similarly, Moody’s indicates that its rated municipal bonds defaulted only 71 times from 1970 to 2011. As shown in the table below, this record of defaults compares very favorably with the corporate bond market, especially given the larger number of issuers in the municipal bond market.
However, not all municipal bonds are rated and the market’s rated universe only tells part of the story. We have developed a more comprehensive municipal default database by merging the default listings of three rating agencies (S&P, Moody’s, and Fitch) with unrated default listings as tracked by Mergent and S&P Capital IQ. Rather than confirming Moody’s 71 listed defaults from 1970 to 2011, our database shows 2,521 defaults during this same period. Similarly, our database indicates 2,366 defaults from 1986 to 2011 versus S&P’s 47 defaults during this same period. In total, we find 2,527 defaults from the period beginning in the late 1950s through 2011. (We don’t have complete information on the number of issues, so we can’t compare default rates.)
Our findings raise the question, What causes such markedly different default frequencies between rated and unrated municipal bonds? Our answer: Not all municipal bonds are created equal. Different types of municipal bonds are secured by very different revenue sources with varying levels of predictability and stability. Furthermore, we believe that rated municipal bonds tend to be self-selected: issuers are less likely to seek ratings if their municipal bonds are not likely to achieve investment grade ratings.