The U.S. economy is about to face a new challenge that has its roots in the arithmetic of growth: That which fiscal stimulus giveth, fiscal stimulus taketh away.

The $1.9 trillion American Rescue Plan enacted in March, as well as a $900 billion pandemic aid package passed in December, are heavily front-loaded. They were set up to get money out the door fast. But one consequence of that strategy is that fiscal policy in the quarters ahead will subtract from economic growth.

Economists mostly project that the economy, with strong momentum in the labor market and huge pools of pent-up savings by households, will be strong enough to keep growing despite the fading of the fiscal boost. To avoid an economic downturn, a huge handoff must occur from government-driven demand to the private sector.

The mainstream view is that this will be successful. But there are aspects of this unusual economic moment that could make the road ahead bumpy.

There is no modern precedent for such huge swings in sums the government is pumping into the economy. And there is a risk — recently acknowledged by a top Federal Reserve official — that if pandemic-era savings are disproportionately held by the affluent, they will sit on that cash rather than spend it.

“We’re definitely going to see a huge drop-off in fiscal stimulus,” said Nancy Vanden Houten, lead economist at Oxford Economics. “The question then is how well positioned is the economy to deal with that, and we don’t really know for sure, which applies to so much about this period we’re going through.”

Most Americans who were to receive stimulus checks of a combined $2,000 per person have already gotten them. The Treasury Department said this month that $395 billion of that cash is now shipped, which is slightly more than the payments in the American Rescue Plan were projected to cost when it was passed.

While unemployment insurance payments remain elevated, that spending is also tapering as people return to work — and supplements to those payments are scheduled to expire in September. Much of the other spending was either near-term, focused on things like vaccine rollout, or will be spent very gradually, such as on an expanded child tax credit and grants to state and local governments.

Overall, government spending added 8.5 percentage points to the economic growth rate in the first quarter, according to calculations by the Hutchins Center on Fiscal and Monetary Policy at the Brookings Institution. But that fiscal impact is forecast to turn slightly negative in the second and third quarters — and then act as a meaningful drag on growth in the fourth quarter of 2021 and in 2022.

By the second quarter of 2022, fiscal policy is on track to subtract 3.3 percentage points from the growth rate, considerably more than the 2.2-percentage-point subtraction in the third quarter of 2011, which was the most extreme quarter in the last post-stimulus hangover of the previous recession.

That could change depending on where negotiations on infrastructure and family support policies lead, but those policies would be expected to influence fiscal policy over many years — they are backloaded rather than front-loaded — so they should not radically change the near-term future.

The case for staying calm even as federal spending plummets rests on the rapid growth of the private sector in recent months.

Employers are adding to their payrolls at a breakneck pace, so rising compensation ought to prop up consumer spending even as government support goes away. Businesses report being in an expansionary mood, which bodes well for investment spending. And overseas economies should start to surge ahead as other countries achieve more widespread vaccination, which would be good news for American exports.

“I think the basic story is that the economy is reopening, so it can take the fact that this stimulus is coming off,” said Louise Sheiner, a senior fellow at Brookings.

Moreover, Americans are sitting on a vast pool of savings from money they did not spend on things like travel and restaurants during the pandemic. Households have saved an average of $282 billion per month since March 2020, compared with $103 billion a month in 2019.

So a big question for the economy in the second half of 2021 and 2022 is what happens to that cumulative additional savings of $2.5 trillion. Will it prop up near-term spending enough to keep growth on a strong track, or will Americans instead prefer the comfort of having a beefed-up balance sheet?

That is where the distributional concern arises. To the degree that money is held by people who are financially well-off, they may be less likely to spend it and help propel the economy.

“Today’s fiscal tail winds are projected to shift to headwinds next year,” Lael Brainard, a Fed governor, said in a speech this month. “So an important question is how much household spending will continue to support growth into next year, as opposed to settling back to pre-pandemic trends.”

On the other hand, the rapidly shrinking fiscal surge could help moderate the inflation pressures that have been building in the economy. Whatever you think of the decision to send $2,000 to people, there will not be any more checks that might push demand still higher and risk fueling a cycle of inflation.

Ultimately, this is another example of the ways the pandemic-driven economy is an unusual one. The only real historical comparisons to the kinds of surges in government spending of the past five quarters involve the beginnings and ends of wars, which have their own economic dynamics.

Which means it is worth watching exactly what happens as the federal government pulls back, and whether American consumers and businesses and importers from around the world step up the way forecasters expect.

This article originally appeared in The New York Times.

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