Nvidia tumbles as U.S. stock market starts September sell-off

NEW YORK (Reuters) -- U.S. stocks slumped on Tuesday, at the start of one of the market's historically worst months, ahead of data likely to influence how much the Federal Reserve will lower interest rates.

The benchmark S&P 500 index, Nasdaq Composite Index and Dow Jones Industrial Average recorded their biggest daily percentage declines since early August. Nine out of 11 S&P 500 sectors fell, led by declines in technology, energy, communication services and materials.

Market sentiment weakened as Institute for Supply Management data on Tuesday showed U.S. manufacturing remained subdued despite a modest improvement in August from an eight-month low in July.

September is widely regarded as one of the worst months for stock market performance based on data stretching back to the 1950s, said Jason Browne, president at Alexis Investment Partners in Montgomery, Texas.

"We had a weak ISM report come out this morning, but we do believe seasonality is a big factor here, especially when you've had such a solid performance for the year until the end of last month," Browne said.

"Everybody is reporting about how September is such a horrible month, and that tends to feed on itself."

The so-called Magnificent Seven megacap technology stocks, which have led this year's rally, slumped. Nvidia dropped nearly 10%, shedding a record $279 billion from its market capitalization, which ended at $2.65 trillion. That is the biggest ever single-day decline in market value for a U.S. company.

Alphabet fell 3.6%, Apple lost 2.7% and Microsoft shed 1.8%. The Philadelphia SE Semiconductor index fell 7.8%.

The Dow fell 626.15 points, or 1.51%, to 40,936.93, the S&P 500 dropped 119.47 points, or 2.12%, to 5,528.93, and the Nasdaq Composite slid 577.33