The data in that report came before the government shutdown had stretched to nearly a month. Now the longest in United States history, the closing will start to take a toll. The latest estimates from the White House’s own Council of Economic Advisers suggest that the shutdown has already knocked almost half a percentage point off the economy’s growth rate, though that drag should end once the government reopens.

The shutdown is affecting some large businesses already. On Tuesday, Delta Air Lines cautioned that reduced travel by government officials and contractors would hurt its sales growth, at a rate of about $25 million a month. JPMorgan Chase executives noted that if the Securities and Exchange Commission — currently closed except for emergency matters — was not able to give approvals for stock market share offerings, and mergers went unapproved by other government agencies, it could cut fee revenue for its investment banking operations.

Profits at American companies may be hurt by the United States’ trade war with China. Evidence that it is slowing global growth mounted this past week, with Germany reporting its slowest annual growth rate since 2013 and China saying that exports fell last month.

Companies in the S&P 500 generate 37 percent of their sales, on average, from markets outside the United States, according to the data provider FactSet, and businesses that have increased their exposure to global economies now look vulnerable.

But for the most part, stock investors have shrugged off these concerns in January, now that they see the Fed as less eager to raise rates.

The Fed had spooked investors as recently as Dec. 19, when it raised interest rates, and its chairman, Mr. Powell, said he didn’t see a need for the central bank to change the way it has been slowly selling off the bonds it bought to bolster the economy over the last decade. The stock market slid 6 percent in the days afterward.

“Clearly the market was skittish about, primarily, the Fed,” said Alicia Levine, chief strategist at BNY Mellon Investment Management. “It sounded like the Fed was on autopilot.”