When borrowers fail to keep up payments on mortgages in the pool that supports asset-backed loans, Fannie and Freddie must buy back the loan.

ECONOMIST: Fannie Mae and Freddie Mac

The goose of course is a corporation or rental property or any other capital asset that produces a relatively predictable flow of the goods or services demanded by an ever growing pool of retirees.

FORBES: 6 Reasons Why I Don't Invest In The U.S. Stock Market