about the credit risk of mortgage borrowers than investors do. During our sample
period, it would have been difficult and expensive for investors to examine the credit
risk of each mortgage in a pool. This gave banks an incentive to have the mortgages in
a pool be riskier than investors thought. Many claim that this is what happened with
subprime MBS in the U.S. during our sample period (e.g., Keys, et. al, 2010). Going
forward, although not in our sample period, there is likely to be more attention paid to
structuring MBS to reduce moral hazard.19
As an alternative, banks can choose to issue
CB where this moral hazard is limited because if a mortgage defaults, the bank must
transfer a replacement loan from its general portfolio to the mortgage pool, thus
restricting the potential gains from fooling investors.