Many have argued that certain types of mortgage securitization contribute to moral hazard. Mortgage securitization enables mortgage originators to pass on the risk that the mortgages they originate might default and not hold the mortgages on their balance sheets and assume the risk. In one kind of mortgage securitization, known as "agency securitizations," default risk is retained by the securitizing agency that buys the mortgages from originators. These agencies thus have an incentive to monitor originators and check loan quality. "Agency securitizations" refer to securitizations by either Ginnie Mae, a government agency, or by Fannie Mae and Freddie Mac, both for-profit government-sponsored enterprises. They are similar to the "covered bonds" that are commonly used in Western Europe in that the securitizing agency retains default risk. Under both models, investors take on only interest-rate risk, not default risk.