The year is not starting off well on Wall Street.

Stocks plunged on Thursday as investors confronted new indications of the depth of subprime losses and housing woes. The Dow Jones industrial average lost more than 300 points, bringing its decline to 15 percent since its peak in October.

Since Jan. 1 alone, the Standard & Poor’s 500-stock index, a broad measure of the financial markets, is down more than 9 percent. And the Russell 2000 index, which tracks small companies, is now officially in a bear market, 20 percent below its peak.

A dismal report on manufacturing activity caught investors by surprise on Thursday morning, sending the main indexes into the red after an early stint in positive territory.

The report, from the Federal Reserve, found that Philadelphia-area manufacturers had contracted much more than expected in a January survey, reaching a six-year low. A similar drop in the index occurred in early 2001, just before the onset of the last recession.