The Government Sponsored Entities, or GSEs, responsible for buying mortgages and packaging them as mortgage-backed securities (MBSs) are well known to have been at the center of the subprime mortgage crisis. The Federal National Mortgage Association (FNMA) and the Federal Home Loan Mortgage Corporation, colloquially known as Fannie Mae and Freddie Mac, were accused of lowering their underwriting standards to encourage subprime lending.