What Did Trump’s Tax Cuts Do?

Seven years ago, when Republicans passed the most significant overhaul of the tax code in a generation, they were sure the law would supercharge investment, raise wages and shift the American economy into a higher gear.

So did it?

The answer, at least for now, is largely lost to history.

A pandemic and a surge in inflation convulsed the global economy not long after the law passed in 2017, scrambling the data that analysts would have typically relied on to draw conclusions about whether the tax cuts helped the economy grow the way Republicans had promised.

As a result, policymakers in Washington are now relying on only a partial understanding of the law’s past as they weigh committing roughly $5 trillion toward continuing it.

“Basically, from 2020 the data is kind of useless,” said Alan Auerbach, an economics professor at the University of California, Berkeley, who counts Kevin Hassett, a top economic adviser to President-elect Donald J. Trump, among his former students.

Economists have focused on just two years before the coronavirus pandemic, 2018 and 2019, to measure the law’s consequences for the most important economy in the world. But that’s a limited window for trying to discern whether the tax cuts prompted a cycle of investment and growth that can take years to play out.

“In terms of looking at longer-run effects, pretty much just forget about it,” Mr. Auerbach said. “There’s just no way to control for the effects of Covid.”