so ta retail bank sells the mortgage and then the retail banks flips it to Fannie Mae and Freddie Mac which essentially package huge numbers of the mortgages across the countries.

所以商业零售银行发行贷款，they…,然后商业零售银行将贷款转手,卖给房地美和房利美,事实上是收集了,大量的,全国的房贷。

斯坦福公开课 - 经济学课程节选