The cost of fixing Fannie Mae and Freddie Mac, the mortgage companies that last year bought or guaranteed three-quarters of all US home loans, will be at least $160bn and could grow to as much as $1trn after the biggest bailout in American history. Fannie and Freddie, now 80% owned by US taxpayers, already have drawn $145bn from an unlimited line of government credit granted to ensure that home buyers can get loans while the private housing-finance industry is moribund.