Open market purchases raise bond prices, and open market sales lower bond prices. So, open market operations (OMOs) affect bond prices.Demand for the bond would decline, and the yield would rise until supply and demand reached a new equilibrium. The Effect of Monetary Policy on Bond Yields. In the municipal market, where demand for bonds has slacked amid mutual fund redemptions, prices in the secondary market fell for the second consecutive day. Under the laws of the Commonwealth of.