The S&P 500 ended March with its steepest monthly decline in more than two years, driven by uncertainty about the scope of President Donald Trump’s tariffs, which investors fear could accelerate inflation, slow consumer spending and stall the U.S. economy.

After a choppy session Monday in which the index ended higher for the day, the S&P 500 registered a 5.8% decline in March, its worst month since December 2022, when the Federal Reserve embarked upon a series of sharp interest rate increases as it sought to tame inflation. The decline in March caps off the S&P 500’s worst quarter at the start of a president’s term since President Barack Obama took over during the 2009 financial crisis.

The benchmark is now down 8.7% from its mid-February peak, a downturn that is near a 10% “correction,” denting the values of portfolios and retirement funds across both Wall Street and Main Street. The technology-heavy Nasdaq Composite index, which has already slipped into a correction, ended the month down 8.2%.

Since taking office a little over two months ago, Trump has kept investors and companies guessing with a haphazard rollout of what he calls an “America first” trade policy. He has threatened, imposed and in some cases then paused the start of new tariffs on goods coming into the United States.

Whiplash over trade policy has fueled market volatility in the first few months of the year. Trump’s next round of tariffs, set to be unveiled Wednesday, could bring additional market swings in the coming days.

“That’s what the market is hoping for after April 2: Give us what you’re going to give us, tell us what’s going to happen, and we will then try to figure it out,” said Steve Sosnick, chief strategist at Interactive Brokers. “But until then, it’s very difficult to invest.”

Stocks had rallied in the wake of Trump’s election, buoyed by Wall Street’s hopes for deregulation and tax cuts. But the postelection rally lost steam as tariffs began to take center stage in Trump’s early economic policy priorities.

More recently, Trump has acknowledged but dismissed the potential financial hit to consumers and businesses from sweeping tariffs, eroding hopes that shaky markets would cause him to reconsider his actions.

— New York Times

Musk consolidates X, xAI in internal move

Elon Musk said that he has sold X, his social media company, to xAI, his artificial intelligence startup, in an unusual arrangement that shows the financial maneuvering inside the business empire of the world’s richest man.

The all-stock deal valued xAI at $80 billion and X at $33 billion, Musk said on X. X’s price was down from the $44 billion that Musk paid for the social media company in 2022, but higher than the $12 billion valuation that some of X’s investors have recently assigned it. The last valuation of xAI, at a December fundraising round, was about $40 billion.

Both companies are privately held and already share significant resources, such as engineers. A chatbot called Grok, made by xAI, is trained on data posted by X users and is available on X. Last month, bankers for X told investors that some of the social media company’s revenue came from xAI.

Musk wrote in his post that “xAI and X’s futures are intertwined.”

Rocket expands its mortgage empire

The mortgage company Rocket is buying competitor Mr. Cooper in an all-stock deal valued at $9.4 billion, just weeks after acquiring real estate listing company Redfin.

Rocket Cos. said Monday that bringing Mr. Cooper Group Inc. into the fold will create a business representing one in every six mortgages in the United States and give it almost 7 million additional clients. The deal will boost loan volumes, the company said, while lowering client acquisition costs.

The U.S. housing market has been slumping for years with homebuyers, and sellers, buffeted by soaring mortgages rates and sky high prices that have put homes out of reach for many Americans.

— From news services