Ryan Brooks.

President Trump came into office promising an economic boom fueled by infrastructure spending, health care reform and tax cuts. But nearly five months later, the excitement over the president's plans has given way to unease, with recent data sounding a note of caution about just how long the economy’s current expansion will run.

On Friday morning, federal economists reported that U.S. job growth came in below expectations in May, with employers adding just 138,000 jobs in the month, below the average monthly gains of 180,000 in the past year. New revisions to the data of the past two months also removed 66,000 jobs from the rolls.

Wage growth remained sluggish in May. The unemployment rate fell to 4.3 percent, the lowest it has been in more than 16 years, but it dipped for what economists described as the “wrong reasons” — a contraction in the labor force. The unemployment rate measures only those who are actively looking for work but can’t find it, so it may decline when people stop looking for work.

One negative reading does not constitute a trend, and economists caution that the economy generally remains healthy more than 96 months into the current economic expansion. Market response to the May jobs report was muted Friday, with the Dow Jones industrial average up 62 points.

But there are reasons for caution. What fuels the economy is not just the buying and selling of goods and services, economists say. It’s also the hopes and expectations that businesses and consumers have for the future.

Business leaders’ faith in Trump’s ability to deliver on what they saw as the pro-growth part of his agenda has faded, with few signs of progress toward tax reform or a broad deal on infrastructure. The parts of Trump’s agenda that business leaders feared, however, have made more headway, including a crackdown on immigration and a more protectionist stance toward foreign trading partners.

“The negative economic proposals have become more likely than the positive ones,” said Mark Hamrick, senior economic analyst at Bankrate.com.

Furthermore, the current readings fall far short of the kind of growth that the Trump administration is looking for to support its tax cuts and other policy proposals. Trump has pledged to boost the economy to 3 percent growth — an estimate which is baked into the administration’s budget proposal — and generate 10 million jobs in his first term.

“The bloom is off the stimulus package,” said Diane Swonk, a Chicago-based economist. “Those who thought there would be health care, infrastructure reform and tax cuts are going to be very disappointed.”

Meanwhile, other economic data, such as stubbornly low wages and inflation, are calling into question the Federal Reserve’s plan to continue raising interest rates as part of the easing of its efforts to stimulate the economy.

Fed officials have said that they expected to raise interest rates three times this year if the progress in the economy met their expectations. The central bank lifted rates at its meeting in March, and traders widely expect it to lift them again at a meeting in mid-June.

But weaker economic data — especially the lack of wage growth, which would signal that inflation is just around the corner — could encourage the Fed to proceed more cautiously with rate increases later this year.

The data “will put many Fed officials on alert for more signs of economic disappointment ahead,” said Scott Anderson, an economist at Bank of the West.

Meanwhile, consumer and business confidence have dipped slightly since the election. They remain near historical highs, but economists say that continued uncertainty over how the Trump administration’s policies will unfold is affecting the economy.

Cathy Barrera, the chief economic adviser for ZipRecruiter, a jobs search site, says that her company’s surveys show that while employers at small and medium companies are optimistic about potential tax cuts and deregulation, they are holding off on decisions to hire until they see real results.

“We’re not necessarily seeing those intentions and optimism translate into hires,” Barrera said.

Widespread confidence has fueled U.S. stock markets to all-time highs. But the economy could face challenges later this year that will test the market’s optimism.

Treasury Secretary Steven Mnuchin has called for Congress to raise the debt ceiling before departing for their August recess, to prevent the government from running out of money. But Republicans appear divided over whether to prioritize shrinking the deficit or enhancing the military.

With the debt ceiling looming large, the prospect of real progress on health care or tax reform this year appears to be diminishing.

These delays have real costs. Tax experts report that some Americans are still putting off payments to the government in case Trump can deliver on his promise of dramatic tax cuts. For example, some are choosing not to sell assets that would incur a capital gains tax, which Trump has promised to lower.

That appears to be affecting the revenues collected by the state and federal governments, and speeding the approach of the point at which Congress must raise or suspend the debt ceiling, or the government runs out of money.

Swonk, the Chicago economist, says that policy changes may also be putting a damper on hiring in the health-care sector, a substantial source of well-paying jobs for the economy. While the sector added 24,000 jobs in May, Swonk says that is down from last year, reflecting uncertainty about who will be covered under future health-care plans.

The president’s decision this week to withdraw from the Paris accord on climate change may also be keeping businesses in the fossil fuel and alternative energy industry guessing about the future investment environment.

While businesses generally favor the prospect of deregulation, Mark Zandi, chief economist at Moody’s Analytics, says that certainty may now be more valuable.

“There’s a mantra that less regulation is good. I think more importantly, it’s stable regulation,” he said.

“If it’s swinging with whomever has the reins of government, that’s a problem for businesses. It’s a problem if they don’t know what the world’s going to look like when their investment comes to fruition.”