Traditional investing logic would indicate that the rally in bonds is overdue for a reversal, but investors may have to continue to wait for any such turn.They can thank or blame pension funds, depending on their perspective. These funds now oversee more than $18.6 trillion, a volume of assets that's bigger than annual U.S. economic output, according to Federal Reserve data. And they're increasingly plowing their money into debt, including money newly raised through increased taxes.