Any debt-based economy, whether the Fed, the ECB, the IMF, etc. is a pyramid scheme. It works only if ever-widening populations of new borrowers can be found to take out loans for homes, school, medical care, cars. etc. to allow creation of new money which circulates through commerce until it is used to pay the interest on the old money. But, and here is the trap, total aggregate debt always outstrips the total aggregate money in circulation. When new borrowers cannot be found, the system, starts to come apart. At that point, Keynesian economics says that the government has to step in and borrow on behalf of the citizens who have stopped borrowing, to keep plunging them deeper into debt to the bankers.