At the closing, the Dow Jones index lost more than 800 points and decreased by 1.66 percent to 48,804.06 points.
The S&P 500 index decreased by 1.04 percent to 6,837.75 points and the Nasdaq index decreased by 1.13 percent to 22,627.27 points.
While tariff uncertainty and concerns about artificial intelligence in the USA reduced investors’ risk appetite, a negative trend was observed in equity markets on the first trading day of the week.
The US Supreme Court ruled on February 20 that the International Emergency Economic Powers Act (IEEPA), on which the tariffs put into effect by President Donald Trump were based, did not give the president the authority to impose tariffs.
The court did not make a clear ruling on whether the government should refund the customs duties it received.
That same day, Trump imposed a 10 percent global tariff on top of those already imposed under Section 122 of the Trade Act of 1974, pointing out that there were alternative methods for imposing tariffs.
Trump announced on his social media account on Saturday that he would increase these tariffs to 15 percent.
Threatening new tariffs on trade partners, Trump said, “Countries that want to ‘play games’ with the Supreme Court’s absurd decision, especially those that have ‘scammed’ the United States for years, even decades, will soon face a much higher and worse tariff rate than they accepted.”
Analysts said that new developments regarding customs duties increased market uncertainty regarding inflation and the global growth outlook.
Analysts pointed out that the market ups and downs related to tariffs showed less fluctuation compared to the first shock in April last year, but stated that this could still be a cause for concern for the markets for the rest of the year.
On the other hand, the decline in the shares of companies related to software and cyber security attracted attention after the artificial intelligence company Anthropic announced new programming capabilities for its “Claude Code” product.
Shares of CrowdStrike, which provides cyber security solutions, fell by nearly 10 percent, shares of Zscaler fell by more than 10 percent, shares of Okta fell by 6.4 percent and Fortinet’s shares fell by 5.5 percent.
IBM’s shares, which completed the day with a loss of more than 13 percent, were also effective in the decline in the Dow Jones index.
On the macroeconomic data side, the amount of factory orders in the USA decreased by 0.7 percent in December last year.
While the statements of the US Federal Reserve (Fed) officials are also being followed, Fed Board Member Christopher Waller stated that if the data indicating an improvement in the labor market in January continues in February, his view on appropriate monetary policy may shift towards a pause in interest rate cuts at the next meeting.
