Monthly jobs data can be volatile, with big swings already in January, February and March of this year. But the slow pace of hiring in May followed other disappointing indicators. Oil prices and yields on Treasury bonds have both plunged, which suggests traders expect slower growth.

The huge corporate tax cut enacted in late 2017 served as a tailwind for the economy in 2018 and early 2019, but the impact is beginning to fade. In the first five months of 2019, the economy added an average of 164,000 jobs, down from an average gain of 223,000 for all of 2018.

What’s more, retail sales and factory orders declined in April, an indication that consumers and businesses are becoming more cautious. The jobs report on Friday also revised down hiring data in March and April by 75,000.

“Over all, the economy is on a fragile footing,” said Lindsey Piegza , chief economist at the investment bank Stifel. “We’re still talking about solid growth at the start of the year, but that’s in the rearview mirror. The name of the game is uncertainty.”

At big companies, tariffs are the leading cause of those jitters. The Trump administration has been putting pressure on China for months, but tensions increased last month when negotiators failed to reach a deal and the administration raised tariffs on $200 billion worth of Chinese imports.

President Trump threatened Mexico with tariffs on May 30, when he said the administration would place a 5 percent duty on imports from that country to compel it to halt the flow of Central American immigrants to the United States.