The profits engine that made many Americans feel richer than they had in a generation may now be working against them.

The plunge in the S&P 500 index has been caused by companies warning investors about challenges that their businesses are facing and sending their stocks sharply lower.

After investors began to fear that the Federal Reserve would slam the brakes on the economy to tame inflation, the stock market fell. The central bank's moves could hurt corporate earnings.

The investors hope that the Fed can bring down inflation without hurting the economy. The recent slew of lackluster corporate financial reports suggest that the economy has already made a turn for the worse, and that more companies will announce slowdowns in their business.

There is a lot of uncertainty and I think things are going to weaken.

The macroeconomic environment has deteriorated faster than anticipated since we issued guidance on April 21, 2022. Since the news, it's stock is down 31 percent.

Corporate America had a year of record profits.

Many companies in the S&P 500 were helped by loose monetary policy and high government spending. Some businesses posted higher profits because prices for goods that were in high demand and short supply went up a lot, often more than making up for the fact that the companies sold fewer goods.

Corporate profits in the S&P 500 were up 70 percent from 2020 and 33 percent higher than in the previous year, which was a pretty good year.

There was something else that happened last year that created the bonanza.

A New York Times analysis of over 2,000 publicly traded companies outside the financial sector found that most of them increased sales faster than expenses, a remarkable feat when the cost of wages, raw materials and components was rising.

The profit margins, which measure how much money a business makes on each dollar of sales, rose well above the average. Companies made an estimated $200 billion in additional operating profits last year because of the increase in margins.

The windfall sent stocks surging in a wave of market exuberance but may have been beyond what business fundamentals merited. The price-to-earnings ratio for all of the companies in the S&P 500 increased to 23 at its peak, compared with an average of 18. Stock prices were vulnerable to a sell-off at such an elevated price-to-earnings ratio.

There are good reasons for investors to be concerned about profits. Many federal programs created during the Pandemic have ended. The interest rates are being raised by the Fed. The supply chain problems that may have helped them boost profits last year have become a burden.

Deere said that it lacked parts to complete certain products, and that materials costs were still rising. The company that makes computer networking equipment complained that it couldn't get certain components.

Demand for some goods and services is flattening or falling, which is worrisome to investors. Walmart said that higher food costs appeared to have reduced demand for other items. Brian Cornell, Target's chief executive, said that the company didn't anticipate the magnitude of the shift in demand for things like apparel and home goods.

Gap's shares fell sharply last week after it announced disappointing earnings for the first three months of the year, as well as a more pessimistic outlook for its profits through the rest of the year. The Old Navy brand has suffered a decline in sales, which tends to appeal to lower-income consumers because it carries lower-priced merchandise than Gap stores.

Whether it was last year in Covid or this year in Gap, we are dealing with really volatile consumer signals.

Retailers are being pushed to discount goods because of larger inventories and lower sales. As prices for some goods fall back to earth, profits could be good news for the inflation outlook.

Many companies did well in the first three months of the year and have offered optimistic projections for the rest of the year.

According to S&P, only 97 of the companies in the S&P 500 reported earnings that fell short of analysts' expectations.

The stock of Macy's and Dollar General jumped on Thursday after the companies gave optimistic outlooks. The retail chain increased its profits forecast.

There was no drop-off in demand for Deere's products, even though the company warned about supply chain problems.

Wall Street analysts are generally optimistic. They have changed their projections for some sectors, but increased them for others. According to data from FactSet, the analysts have increased their forecasts for the earnings of the companies in the S&P 500 and expect them to rise 10 percent this year and next.

Mr. O'Rourke said analysts usually didn't cut estimates until the business was starting to sour. Second-quarter earnings are reported in July.

Analysts know the numbers have to come down.

Many analysts and corporate executives say they are not concerned about demand. Even with higher interest rates, people and businesses have plenty of money to buy goods and services.

A survey done by the Fed in the fall showed that there was a dichotomy between weak consumer sentiment and solid household bank accounts.

The Fed found that the percentage of adults who said they had the money to cover a $400 emergency expense had reached its highest level since the polling question began. Fed officials wouldn't speculate on the effects of high inflation.

Recent data has alleviated fears that spikes in food and fuel costs could force American families to pull back on discretionary purchases. Industrial production rose to a record level last month, while retail sales climbed to a new high.

Lower-income households have used up a lot of their savings, but it is possible that higher-income households can help sustain consumer spending. The coronaviruses have generally faded as a life-changing concern for many families, so many people are eager to travel. United Airlines, Southwest Airlines and JetBlue said this month that their second-quarter revenue would be higher than they had expected.

Lower-income households accounted for a relatively small share of consumption in the economy even though they would be hit the hardest by inflation. The analysts found that households in the bottom 60 percent of income distribution account for less than 40 percent of total expenditures, while the top 40 percent make up more than 60 percent of spending.

Jim Paulsen, chief market strategist at the Leuthold Group, said that financial conditions had been tightening for a while and that inflation was likely to moderate soon. He said it would make consumers feel better about the economy and give them more purchasing power.

Mr. Paulsen said that a good news could send stocks higher. That is where bears die.

The S&P 500 closed up 6.6 percent last week.