Donald Trump has celebrated the success of his efforts to prevent Carrier Corp. from moving jobs out of the country, and the people in Indiana whose jobs he saved will, justifiably, celebrate along with him. But this isn't simply a case of closing the barn door after all of the horses have escaped. It's a case of closing the barn door decades after the horses were traded in for new automobiles.

About a month before Election Day there was an essay in the New York Times questioning why manufacturing held such an outsized role in American policy arguments. The essay's author pointed to Pittsburgh, a city in which there are literally robot cars serving as taxis and in which the largest employer is a regional hospital. Yet Pittsburgh's perception nationally is as a down-on-its-luck manufacturing hub. That perception holds true across much of the Rust Belt and it powered a lot of the understanding of what happened after the votes were tallied in the presidential election.

One point of that essay is that the perception is very much out of date. Manufacturing has made up a smaller and smaller part of the American economic picture for decades, extending well before offshoring of steel production and NAFTA.

Why? As the Brookings Institution noted earlier this month, it's in large part because of automation improvements. This graph tells the story: Huge increases in production in manufacturing while requiring fewer people.

"The return of more manufacturing won’t bring back many jobs because the labor is increasingly being done by robots," says Mark Muro of Brookings' Metropolitan Policy Program. This is the point made by Sen. Ben Sasse (R-Neb.) on Twitter this morning. "Automation -- even more than trade -- will continue to shrink the number of manufacturing jobs," he wrote. "This trend is irreversible."

But this is the theme of Trump's presidential pitch. Make America great again. Reverse those inexorable trends -- or at least promise to. Bring back the long-gone days misted with nostalgia. Bring back that old Pittsburgh that we remember fondly.

It was natural that Indiana would be ground zero for this fight for Trump, given that manufacturing is more important in Indiana than in other places.

In Indiana, manufacturing makes up a larger percentage of employment than it does in the country as a whole.

Over the past 25 years, manufacturing elsewhere has slipped more than it has in Indiana, so Indiana's manufacturing jobs make up more of all of the jobs in the country than the state once did.

Trump has another specific reason to focus on the state. Trump -- and, probably more importantly, Mike Pence, the state's soon-to-be-former-governor -- managed to make the deal with United Technologies (the parent company to Carrier) by offering up $7 million in tax breaks. As Business Insider's Josh Barro notes, this is an approximate cost of about $900 per worker per year for the state, a relatively good investment. But it requires the acquiescence of the state.

Political opponents of the president-elect were also quick to point out that this is the opposite of what Trump promised he'd do in situations like this. He'd threatened to use the stick of higher taxes, not $7 million worth of carrots. The risk Trump faces is that companies now know that threatening to move jobs overseas may be of economic benefit to them. Companies have played states off of one another for years by making similar threats. (There are also valid questions about the extent to which the government should intervene in the free market for political purposes, but we'll set those aside for now.)

Again, while this is unquestionably good news for those 1,000 people, it doesn't change the fact that the economy is different today than it was back when America was "great." Our Wonkblog colleagues note that it would take hundreds of deals like the one with Carrier to offset manufacturing jobs lost since 2000. The industry is vanishing, as surely as America itself is changing.

That's not what Trump ran on and that's not why many of Trump's voters backed him. They want him to stop the grains in the hourglass or, better, to get them to float back up into the upper bulb. They want him to make America great again.

For the American economy to stay great, though, Trump needs to figure out where it's going, not try to force it back to where it was.