Senator BIRMINGHAM (South Australia) (14:25): Mr President, I ask a further supplementary question. I note the minister's references to so-called compensation and refer the minister to the statements in Budget Paper No. 1 that any changes in the carbon tax will affect receipts but that the costs of household assistance are permanent. Minister, what risks are there to the budget bottom line if the government has got any of its other forecasts as wrong as it got the original forecast that 1,000 entities would be paying and liable for the carbon tax?