The U.S. stock market keeps setting records as AI excitement keeps building

Specialist Michael Gagliano, left, and trader Timothy Nick work on the floor of the New York Stock Exchange, Wednesday, Sept. 17, 2025. (AP Photo/Richard Drew)

NEW YORK — Wall Street keeps setting more records, and excitement about the artificial-intelligence industry keeps leading the way.

The S&P 500 climbed 0.4 per cent to set an all-time high following mixed trading on Monday. The Dow Jones Industrial Average dipped 63 points, or 0.1 per cent, while the Nasdaq composite rose 0.7 per cent to its own record.

Advanced Micro Devices helped lead the way and soared 23.7 per cent after announcing a deal where OpenAI will use its chips to power AI infrastructure. As part of the deal, OpenAI could own up to 160 million shares of AMD if it hits certain milestones.

A frenzy around AI has been one of the main reasons Wall Street has been hitting record after record, though that’s also raising worries that prices have potentially shot too high. Much of the furor around AI in the last couple weeks has come from OpenAI, which has quickly grown into a US$500 billion company. It’s been announcing deals with businesses around the world to develop more AI infrastructure.

Another chip company, Nvidia, announced a deal last month where it would invest US$100 billion in OpenAI as part of a partnership, creating criticism that the AI investment pipeline was beginning to appear like a circle. Nvidia slipped 1.1 per cent following the AMD announcement. Because it’s the most valuable stock on Wall Street, Nvidia was the heaviest weight on the S&P 500.

Outside of tech, Comerica jumped 13.7 per cent after Fifth Third Bancorp agreed to buy it in an all-stock deal valued at US$10.9 billion. The combination would create the country’s ninth-largest bank. Fifth Third’s stock fell 1.4 per cent.

Tesla rose 5.4 per cent after social-media postings by the electric-vehicle maker hinted at a possible product unveiling coming on Tuesday.

Verizon Communications fell 5.1 per cent after the telecom replaced its chief executive. Dan Schulman, a director at the company and former CEO of PayPal, is taking over for Hans Vestburg.

Elsewhere on Wall Street, trading was relatively quiet as the stock market continues to largely ignore the U.S. government’s shutdown. Past closures of the federal government have had minimal effect on the stock market or on the economy, and the bet on Wall Street is that something similar will happen again.

All told, the S&P 500 rose 24.49 points to 6,740.28. The Dow Jones Industrial Average fell 63.31 to 46,694.97, and the Nasdaq composite rose 161.16 to 22,941.67.

Politics are playing a bigger role in stock markets abroad, as Japanese stocks soared and French stocks slumped following their latest political shake-ups.

Japan’s Nikkei 225 jumped 4.8 per cent after the country’s Liberal Democratic Party chose Sanae Takaichi as its leader. She was an ally of the late Prime Minister Shinzo Abe, who pushed for lower interest rates and other policies that investors liked.

The yen’s value dropped against the U.S. dollar on expectations that Takaichi will boost spending, likely adding to inflationary pressures. That in turn helped push up stocks of Japanese exporters, whose products can become more attractive on the global market when the yen is cheaper.

“Obviously, investors like what she has been saying and certainly today judging by the number of stocks that moved and which stocks moved, it seems like pretty much led by foreigners so far,” Neil Newman, head of strategy at Astris Advisory Japan, said about Takaichi.

In Paris, the CAC 40 index slumped 1.4 per cent following the resignation of France’s new prime minister.

Sébastien Lecornu resigned a day after he named his government, drawing a backlash across the political spectrum for his choice of ministers. French politics have been in disarray since President Emmanuel Macron called snap elections last year that produced a deeply fragmented legislature.

In the bond market, the yield on the 10-year Treasury rose to 4.16 per cent from 4.13 per cent late Friday.

The shutdown of the U.S. government likely means delays for U.S. economic reports scheduled for this week, though investors will have some earnings reports to comb through, including from Delta Air Lines, PepsiCo and Levi Strauss.

Despite the shutdown, the Federal Reserve will release minutes from its meeting last month, when it cut its benchmark interest rate for the first time this year. Much on Wall Street is riding on expectations that the Fed will continue cutting interest rates through this year and into next.

___

Stan Choe, The Associated Press. AP Business Writers Matt Ott and Elaine Kurtenbach contributed.