The May 2010 yield on AAA-rated municipal bonds stayed relatively level for 30-year bonds at 4.39% and decreased slightly for 10-year bonds from 3.22% to 3.07%. Yields on 30-year treasuries have fallen more sharply, however, dipping below munis for the first time since last December.

Source: Bloomberg (www.bloomberg.com)

Source: Bloomberg (www.bloomberg.com)