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).