If an investor were to purchase a callable bond, with a coupon of perhaps 5%, while interest rates for similar securities in the market were 4.95%, there would probably be little chance of the bond being called by the issuer. If market rates were 6%, there would be no likelihood of the bond being called. If, on the other hand, rates in the market were 2%, which would allow the bond issuer to borrow more cheaply elsewhere, the issuer would almost certainly call in the bond, and perhaps issue new bonds at, say, 2.25%