new york (Bloomberg) — Willis Group Holdings Ltd., the world's third-largest insurance broker, tumbled the most in seven years in New York trading after posting a 46 percent drop in third-quarter profit and cutting its full-year forecast.

Willis fell 18 perecent to $21.72 at by 2.15 p.m. in New York Stock Exchange composite trading yesterday. That's the biggest drop since June 2001 and the lowest price since January 2002. The shares have lost more than 30 percent this year.

"These are unprecedented times, and we are responding with an appropriate sense of urgency," chief executive officer Joseph Plumeri said.

Insurers and brokers contended with an 11 percent annualised drop during the quarter for commercial insurance rates, which have been falling since 2004, according to the Council of Insurance Agents and Brokers. The decline hurt profit at Willis, and the firm said global economic turmoil has cast doubt on future prices and clients' buying decisions.

Net income for the third quarter fell to $36 million, or 25 cents a share, from $67 million, or 46 cents, a year earlier, the London-based company said in the statement. Profit excluding some items was 32 cents a share, missing the 39-cent average estimate of 10 analysts surveyed by Bloomberg.

Willis reduced its 2008 forecast to a range of $2.60 to $2.70 a share excluding items, from its July 30 forecast of $2.85 to $2.95.

Brokerage revenue rose two percent, excluding the impact of acquisitions and foreign exchange. The international business, which includes markets outside of North America and the UK, rose 10 percent. North American business fell two percent on a "soft insurance market", the company said.