When I look for munis maturing in four or five years, the yield to maturity these days for AA or better is around 3.4% to 3.5%. However, I frequently see a YTM of 3.6% to 3.7%, where the only apparent difference from the surrounding bonds is that the higher yielding bond is actually a longer term bond that is pre-refunded (sometimes to 101 or 102, for example) to the earlier date four or five years from now. There are plenty of examples of this. Why should the market assign a higher yield to a pre-refunded bond with exactly the same rating as the bonds around it? I buy these pre-refunds all the time, but have never understood why they are the bargains they appear to be. Am I missing something?
D.M.