when interest rates decline the issuer is more likely to call the bond in order to replace it 
the bottom lineif you invest in callable bonds you need to know its yield to maturity but it is perhaps more important to know its yield to call yield to call is the return you will get if the issuer decides to essentially cancel the issue and pay off investors early if you want real assurance that you ll get the yield to maturity that you expect consider investing in non callable bonds they pay a bit less than callable bonds but you ll be certain to get the income you expect from them 