Officially, the tax bill passed by the US Senate in the early morning hours of December 2 costs $1.45 trillion over 10 years, or $1 trillion after taking into account its effect on economic growth.

Those are the numbers of the Joint Committee on Taxation, Congress’s official arbiter of tax figures, but skeptics like the Committee for a Responsible Federal Budget have argued that the true cost is substantially higher. If the many temporary provisions of the bill are made permanent (and Republican senators have insisted they will make them permanent), the true cost is more like $1.6 trillion to $2 trillion, and it continues to mount after 10 years are up.

That bill has to be paid for, somehow. Congress could keep rolling over the debt, yes, but historical experience suggests that tax cuts are typically paid for by tax hikes in the future. Republicans have suggested they want to finance the cuts by slashing entitlement programs like Social Security, Medicare, and food stamps. “We're going to have to get back next year at entitlement reform, which is how you tackle the debt and the deficit,” House Speaker Paul Ryan said in a radio interview on Wednesday.

Whether you pay for the $1.5 trillion through tax hikes or spending cuts, that financing changes who ultimately wins and loses under the bill. And a new study by the Tax Policy Center suggests that when you take financing into account, the vast majority of Americans lose out.

When the bill is paid for, it winds up hurting most Americans

Republicans haven’t put out any specifics about the Social Security, Medicare, and other spending cuts they want to use to reduce the deficit. So TPC's William Gale, Surachai Khitatrakun, and Aaron Krupkin present a number of options for how the burden of the spending cuts could be distributed:

Spending could be cut for every household equally. In 2019, paying for the tax cuts in the Senate bill would cost $1,210 per household. This option assumes that federal spending is cut in such a way that the burden is literally equally distributed, with every household receiving $1,210 less benefit from government spending in 2018. Spending could be cut so that the burden is proportional to a household's income. Funding the tax cuts would cost, on average, 1.6 percent of each household's income in 2019. This option assumes spending cuts that match that: so someone making $20,000 a year would see $320 less in government spending go their way, while someone making $1 million would get $16,000 less in spending, and so on. Spending could be cut in a way that’s proportional to individuals' income taxes. Since income taxes are progressive, and many low-income Americans don't pay them at all, this would entail little or no spending cuts that hurt the poor, and a much heavier concentration of cuts harming the top 1 percent.

I should say that the first of these options is, by far, the most likely. The US doesn’t spend a lot of money directly on rich people; our benefits to the affluent tend to come through the tax code, through provisions like lower rates on capital gains, or through the mortgage interest and charitable deductions. That makes scenario 3, which assumes massive cuts to spending programs that benefit the rich, a bit fanciful.

More to the point, Republicans’ efforts to cut spending have focused almost exclusively on programs for the poor, like Medicaid or Supplemental Security Income or food stamps. President Trump’s budget proposal includes $2.1 trillion in cuts to Medicaid, Affordable Care Act subsidies, food stamps, Social Security Disability Insurance, Supplemental Security Income, and cash welfare (TANF). That would go a long way toward paying for tax cuts, and its impact would be even more concentrated on the poor than in scenario 1, where spending is cut equally per capita.

Gale, Khitatrakun, and Krupkin find that the overall distributional impact of the tax cuts depends wildly on which of the scenarios they considered occurs. Here’s the Senate bill, as financed by a $1,210-per-household cut in government spending:

With spending cuts incorporated into the analysis, the bill turns into a rather shocking tax hike on the poor and middle class. The poorest fifth of Americans face an 8.1 percent cut in their income due to loss of government benefits (likely in the form of programs like food stamps and Medicaid). The middle fifth of Americans would be $370 worse off per year. The rich, however, and particularly the 95to to 99th percentiles (households that earn $308,200 to $746,100 a year) get substantial tax cuts still, because $1,210 just isn't a whole lot next to their overall income.

The TPC also modeled what share of households would gain or lose under this plan:

If the bill is financed this way, 71.6 percent of Americans would be worse off, including 99.9 percent of the poorest Americans. By contrast, large majorities of the richest Americans, in particular the 95th to 99th percentiles, would be better off.

If the cuts are proportional to income (which, again, I think is a much less plausible modeling scenario than equal per-household spending cuts), and every household is 1.6 percent of income worse off due to the financing, then 63.9 percent of Americans wind up with a tax increase, including 93.4 percent of the poorest Americans. That’s a little better than the first scenario, but not much.

If the cuts are proportional to income tax burden, and concentrated among the richest Americans who pay the most income taxes, the results are, unsurprisingly, progressive. In that scenario, 65.2 percent of Americans would get a tax cut, while 81 percent of the top 0.1 percent would see a tax hike averaging 3.7 percent of their income, or $273,400 a year. I’ll leave it to you to judge how likely Republicans are to champion such a plan.

Maybe deficits don’t matter

It’s common in economic analysis to assume that the long-run budget deficit a government runs is $0. That is, all budget deficits are eventually financed by budget surpluses in the future, and tax cuts that increase the deficit have to eventually be paid for by tax hikes or spending cuts in the future.

But the “long run” is very long indeed. The US has historically run budget deficits much more often than it’s run surpluses, and the deficits were substantially larger than those rare surpluses as well. Over the span of US history, the country has spent considerably more than it’s taxed.

And maybe that’s okay. The United States isn’t a business whose books need to balance eventually. It’s a permanent government that pays its debts in a currency it controls. If its deficits get too big, that can spur high interest rates and inflation, which have a number of negative consequences. But there have been no signs of either of those problems in recent years.

That’s led a lot of people, like my colleague Matt Yglesias, to grow skeptical of the idea that deficit-financed policies like tax cuts have to be, in some meaningful sense, “paid for.” The Bush tax cuts and the Iraq and Afghanistan wars haven’t really been “paid for” yet in any way. Maybe the Trump tax cuts will be the same.

That’s a fair argument, but it’s not one that Republicans in Congress are making. Their claim, instead, is that they’re going to enact this massive tax cut and then pivot to cutting spending programs, in particular Social Security, Medicare, Medicaid, and food stamps. In that context, it makes sense to consider what such pay-fors would do to the overall distribution of the tax cuts. And what they do is make the tax cuts extremely regressive, and create net tax hikes on the middle class and poor.