The wave of migrants who arrived during the Biden administration fueled some of the anger that propelled Donald J. Trump back to power. They also offset a labor shortage, putting a damper on inflation.

With the next administration vowing to seal the border and carry out the largest deportation program in American history, those economic forces could reverse — depending on the degree to which Mr. Trump can fulfill those promises.

Mr. Trump’s newly appointed “border czar,” Tom Homan, has said that the administration would start with the immigrants who have committed crimes. There are not nearly enough of those to amount to removals on a mass scale, however, and Vice President-elect JD Vance has also said that all 11 million undocumented immigrants should prepare to leave. “If you are in this country illegally in six months, pack your bags, because you’re going home,” Mr. Vance said in September.

The numbers could rise by another 2.7 million if the new administration revokes several types of temporary humanitarian protection, as the Trump adviser Stephen Miller previewed last year. On top of that, millions of undocumented residents live with U.S.-born children or green card holders who could end up leaving the country as well.

There are logistical, legal, diplomatic and — even though Mr. Trump has said there is “no price tag” he wouldn’t direct the government to pay — fiscal obstacles to expelling millions of people who would rather stay. (According to the American Immigration Council, an advocacy group for immigrants, it would cost $315 billion to arrest, detain, and deport all 13.3 million living in the United States illegally or under a revocable temporary status.)

That’s why forecasting a precise impact is impossible at this point. But if Mr. Trump accomplishes anything close to what he has pledged, many economists expect higher prices on goods and services and possibly lower employment rates for American workers.