NEW YORK (AP) – Stocks plummeted Tuesday, hurtling the Dow Jones industrials down more than 500 points as Wall Street succumbed to a global market plunge sparked by growing concerns that the U.S. and Chinese economies are cooling and that equities prices have become overinflated.

A 9 percent slide in Chinese stocks, which came a day after investors sent Shanghai’s benchmark index to a record high close, set the tone for American trading. The Dow began the day falling sharply, and the decline accelerated throughout the course of the session before stocks took a huge plunge in late afternoon as computer-driven sell programs kicked in.

The Dow fell 546.02, or 4.3 percent, to 12,086.06 before recovering some ground in the last hour of trading. Because the worst of the plunge took place after 2:30 p.m., the New York Stock Exchange’s circuit breakers, designed to halt precipitous moves, were not activated.

Investors’ dwindling confidence was knocked down further by data showing that the economy may be decelerating more than anticipated. A Commerce Department report that orders for durable goods in January dropped by the largest amount in three months exacerbated jitters about the direction of the U.S. economy, just a day after former Federal Reserve Chairman Alan Greenspan said the United States may be headed for a recession.

“It looks more and more like the economy is a slow growth economy,” said Michael Strauss, chief economist at Commonfund. “Moderate economic growth is good – an abrupt stop in economic growth scares people.”

The market had been expecting the government on Wednesday to revise its estimate of fourth-quarter GDP growth down to an annual rate of about 2.3 percent from an initial forecast of 3.5 percent, and grew increasingly nervous on Tuesday that the figure could come in even lower.

The housing market, which the Street had been hoping had bottomed out, also looked far from recovery after a Standard & Poor’s index indicated that single-family home prices across the nation were flat in December. A later report from the National Association of Realtors said existing home sales climbed in January by the largest amount in two years, but the data didn’t erase housing-related concerns, as median home prices fell for a sixth straight month.

The Dow was down 360.42, or 2.85 percent, at 12,271.84 in the last hour of trading.

The broader Standard & Poor’s 500 index was down 42.11, or 2.91 percent, at 1,407.26, and the Nasdaq composite index was off 81.34, or 3.25 percent, at 2,423.18.