Municipals-Over-Bonds Spread - MOB

The difference in yields between a municipal bond and a Treasury bond with the same time to maturity. The MOB is sometimes used for determining tax strategies.

Most MOB spread calculations actually use the yield implicit in futures prices for munis and Treasuries listed on the Chicago Board of Trade. The MOB spread is essentially a comparison of the interest rate spread between federal government debt (Treasuries) and state/municipal debt (municipal bonds).