In the longer run, the Fed expects real annual growth in the United States to fall to 1.8 percent. The Congressional Budget Office’s 10-year outlook comes to the same disappointing conclusion.

The Winter’s Tale

Expectations about the first-quarter figure had fluctuated as pieces of the puzzle emerged. Imports fell and exports rose more than expected, narrowing the merchandise trade deficit for the first time in six months. Orders of durable goods remained sluggish, but revived somewhat as commercial aircraft orders surged in March. And although consumers continued to express a lot of confidence, they pulled back on their spending.

Holiday shopping in the final quarter of 2017 had revved up consumer spending — which accounts for more than two-thirds of the nation’s economic activity — to 4 percent. Businesses responded by replenishing depleted inventories. But the shopping surge receded when the new year started; consumer spending grew only 1.1 percent in the first quarter.

Although the tax overhaul promised to increase take-home pay, its effects may have been blunted for several reasons, including the time it took for the Internal Revenue Service to produce updated withholding tables and for payroll managers to adjust their systems. A poll of registered voters done in April and released this week by Politico/Morning Consult found that only about a fifth of those surveyed were noticing more money in their paychecks.

“I think the fact that we didn’t see a big spurt in spending after the tax cut suggests it’s either too early in the game or consumers are going to continue to be a bit cautious,” said Kathy Bostjancic, chief United States financial economist at Oxford Economics. Nonetheless, she added, “I think there is a legitimate question as to how much of the tax cuts get saved to pull down debt, and how much actually gets spent.”

As for business spending, many of the tax incentives were aimed not at immediate investment decisions, but at those in the medium term. “It does take time for that to filter through,” Ms. Bostjancic said. Some businesses may have also sped up their timetables for purchases at the end of 2017 in order to take advantage of bigger deductions before the tax changes went into effect.

For several years, first-quarter growth rates have been weaker than the longer-term trends indicated, only to rebound in later months. This year, the result could reflect a falloff in spending after an unusual surge that followed the havoc wrought by late-summer hurricanes. Severe winter weather could have also slowed consumption. But some analysts wonder if data adjustments are part of the problem.