NEW YORK — After Wall Street saw its biggest losses yesterday since the Sept. 11, 2001, terrorist attacks, investors will be looking at fresh economic data today to see if the plunge was justified.

Investors drove the Dow Jones industrials down more than 400 points yesterday as worries grew that U.S. and Chinese economic growth could hit obstacles, and on the feeling that share prices had soared too high too quickly.

The U.S. government's report today on gross domestic product could either assuage or aggravate those fears — the market is expecting that the Commerce Department will say that GDP grew 2.3 percent in the fourth quarter, less than the initial estimate of 3.5 percent.

Also today, investors expect new data from the Commerce Department to indicate new home sales declined last month, and the latest survey from the Chicago Fed on regional manufacturing will register a reading of 50.0 for February, up from 48.8 in January.

The Chicago Fed report could give the market clues to how well the Institute for Supply Management's index of manufacturing activity for February will perform.

The market is currently predicting that index to come in tomorrow at 50.0, up from 49.3 last month. A reading above 50 indicates expansion, and below 50 indicates contraction.Wall Street could again take cues from overseas trading.

A 9 percent drop in Chinese stocks triggered yesterday's steep fall in the U.S., which followed a long period of stable and steadily rising stock markets that had not seen such a volatile day of trading in several years.

The Dow's decline accelerated throughout yesterday, and stocks saw a huge dip in late afternoon trading as computer-driven sell programs kicked in, and also as a computer glitch caused a delay in the recording of a large number of trades.

The Dow fell 546.20, or 4.3 percent, to 12,086.06 before recovering some ground in the last hour of trading to close down 416.02, or 3.29 percent, at 12,216.24, leaving it in negative territory for the year. Because the worst of the plunge took place after 2:30 p.m., the New York Stock Exchange's trading limits, designed to halt such precipitous moves, were not activated.

It was the Dow's worst point decline since Sept. 17, 2001, the first trading day after the terror attacks, when the blue chips fell 684.81, or 7.13 percent. In percentage terms, it was the biggest decline since March 24, 2003, when the index fell 3.6 percent as investors started getting rattled as U.S. casualties mounted in the early days after the invasion of Iraq.

The Nasdaq composite index fell 96.66, or 3.86 percent, to 2,407.86. The Standard & Poor's 500 index fell 50.33, or 3.47 percent, to 1,399.04.

The S&P reported that the drop across the major U.S. exchanges hit every industry, and that a total of $632 billion was lost in stocks on the exchanges yesterday.

EYES ON ASIA

Stock markets plunged across much of Asia today for a second day amid jitters about a selloff in China's stock market and a worries about a possible slowdown in the Chinese and U.S. economies.

Shares in Tokyo, Hong Kong, Singapore, Malaysia, Australia, New Zealand, the Philippines and Indonesia all tumbled more than 3 percent in morning trading, following dismal overnight losses on Wall Street, the worst since the Sept. 11, 2001, terrorist attacks.

In China, stock modestly recovered from their 9 percent plunge yesterday — their biggest drop in a decade. The Shanghai Composite Index was up 1.2 percent to 2,804.28.

But investors in other Asian markets dumped shares today, with Japan's Nikkei 225 stock index down 644.85 points, or 3.56 percent, to 17,475.07 points at the close of the morning session.

Hong Kong's Hang Seng Index was down 3.8 percent, while Australia's benchmark S&P/ ASX200 index shed 3.5 percent. Indonesian shares lost 5.2 percent, while Philippine stocks plunged 9.4 percent.

Australian Treasurer Peter Costello today predicted the plunge in China's share market would trigger "volatility on equity markets for some time."

But his overall assessment of China's economy was positive, telling reporters the Asian giant would continue to grow, albeit "in fits and starts."

Japan's Chief Cabinet Secretary Yasuhisa Shiozaki tried to quell concerns about the Tokyo market saying the overall fundamentals in Japan were still strong.

"On a broad perspective the corporate sector continues to perform well," Shiozaki said. "A long-term economic recovery is continuing."