White House officials are boasting that President Trump’s budget would balance federal finances in 10 years. Yet despite extreme reductions in spending on health care for the poor, food stamps, education, science and other basic government programs, Trump’s staff could only balance the budget by claiming vague savings and unspecified sources of new revenue — in other words, with trillions of dollars in mystery money.

It is not just that Trump is counting on a rapid acceleration in economic growth that economists believe is unlikely, which the budget projects will yield $2.1 trillion in new revenue ($2,062,000,000,000, to be more exact). Besides that bonus from growth, the budget also assumes that Trump’s tax cuts — which he has said will be the largest in history — would not affect the government’s bottom line at all.

And even with optimistic assumptions about the tax code specifically and the overall economy more broadly, the White House still needed to claim over $1 trillion in unidentified cuts to miscellaneous programs to balance the budget.