The National Bureau also began releasing at the start of 2017 a much broader purchasing managing index. Because that index has never measured a sharp economic slowdown before, its previous low was 52, set in October.

February’s score on the broader index was just 28.9, down from 53 in January.

Wall Street’s jitters extend beyond stocks.

Other measures of the overall health of financial markets and corporate America are beginning to show signs of strain.

The most profound signal about the future of the global economy is that interest rates are plunging to record lows. The yield on the benchmark 10-year United States Treasury bonds fell to about 1.15 percent on Friday, down from 1.9 percent at the start of the year and 2.7 percent one year ago.

Wall Street is also skittish about risky debt. The biggest United States junk-bond fund — iShares iBoxx High-Yield Corporate Bond Exchange Traded Fund, which tracks an index of dollar-denominated risky corporate debt — has plunged by about 4 percent since Feb. 20, data Friday morning showed. The index posted a record outflow on Tuesday as spooked investors pulled nearly $1.6 billion out of the market.

High-yield debt, which is extended to companies viewed as more likely to fall short on payments, is usually the first to go bad if companies run into trouble. If coronavirus makes credit hard to come by and causes cash flows to dry up, for example, firms that are highly leveraged with shaky prospects could fall behind.

Oil prices are also sharply lower.

That means some relief at the pump for motorists this weekend. The national average price of regular gasoline has dropped two cents in the last week, to $2.45 a gallon, according to AAA. One half of that drop came from Thursday to Friday, suggesting the price decline is accelerating.

The nation has 256.4 million barrels of gasoline in stock, 1.4 million barrels more than last year. But the big drop in global oil prices is a much more important factor. At about $45 a barrel, the American benchmark oil price is at its lowest level since December 2018.