7/22T11:40 FNM FRE

The companies have also been unwilling to accept the pain of market prices in acknowledging delinquent loans. 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. But that requires an immediate write-off at a time when the market prices of asset-backed loans are depressed. Instead, the twins sometimes pay the interest into the pool to keep the loans afloat. In Mr Rosner’s view, this merely pushes the losses into the future

In addition, Fannie and Freddie have bought insurance against borrower defaults when the homebuyer lacks a 20% deposit. But the finances of the mortgage insurers do not look that healthy, which may mean the risk ends up back with the siblings. Just as the rescuers need rescuing, so the insurers may need insuring

Indeed, their capital-adequacy requirement was reduced earlier this year so that they could make more of an effort to bolster the housing market

The authorities are keen to avoid nationalisation, which would bring the whole of Fannie’s and Freddie’s debt onto the federal government’s balance sheet. In terms of book-keeping this would almost double the public debt, but that is rather misleading. It would hardly be like issuing $5.2 trillion of new Treasury bonds, because Fannie’s and Freddie’s debt is backed by real assets. Nevertheless, the fear that the taxpayer may have to absorb the GSEs’ debt pushed Treasury bond yields higher. That suggests yet another irony; the debt of the GSEs has been trading as if it were guaranteed by the American government, but the debt of the government was not trading as if Uncle Sam had guaranteed that of the GSEs

The GSEs are not the only liability for the government. IndyMac’s recent collapse is the latest call on the Federal Deposit Insurance Corporation (FDIC). The FDIC has some $53 billion of assets, so it is better funded than most deposit-insurance schemes. But if enough banks got into trouble, the government would be on the hook for any shortfall. The same is true of the Pension Benefit Guaranty Corporation, which insures private sector benefits, but is already $14 billion in deficit.

In the end, the turtle at the bottom of the pile is the American taxpayer. But that suggests that, if Americans are losing money on their houses, pensions or bank accounts, the right answer is to tax them to pay for it. Perhaps it is no surprise that traders in the credit-default swaps market have recently made bets on the unthinkable: that America may default on its debt