Aon Corp., Marsh & McLennan (M&M) and Willis Group Holdings are the top three global brokers, according to a survey by rating agency AM Best's Best Review magazine.

The firms, which all have offices in Bermuda, came out top of the pile, with Aon boasting a brokerage revenue of $6.1 billion in 2007, Marsh a $4.5 billion revenue, and Willis a $2.5 billion one.

Overall the multi-billion dollar world insurance brokerage business increased to an even greater volume last year, with Best's report, which is in its third year, reflecting brokerage revenues instead of total revenues for the leading 20 companies.

Aon's brokerage revenues rose from $5.6 billion to $6.1 billion between 2006 and last year, while total revenues last year stood at $9 billion.

The company, which is run by president and chief executive officer Greg Case and is based in Chicago, specialising in property and casualty, construction, directors and officers, treaty and facultative reinsurance, divested its underwriting business and combined its global insurance and brokerage operations into a single entity, Aon Risk Services.

Meanwhile it also completed 21 acquisitions and repurchased $751 million of its common stock and plans to continue to deliver positive growth, expanding profit margins and improve earnings per share as part of its strategy for the next two years.

Marsh, which is headed by Bermudian Brian Duperreault and headquartered in New York, focuses more on the commercial side of the business.

Last year's highlights included the appointment of Daniel Glaser as chairman and CEO of Marsh Inc., M&M's insurance brokerage subsidiary, while it also sold Putnam Investments to Great-west Lifeco. During this year and the next its strategy is to deliver client value and drive profitability and growth by capitalising on global reach and market expertise.

London-based Willis, another specialist in the commercial, reinsurance, construction, aerospace, energy, financial and executive risks, employee benefits, health care and environmental fields, list its acquisition of InsuranceNoodle, an Internet distributor of US small business insurance, as one of its main achievements.

During 2008 and 2009, it plans to execute on its 'shaping our future' strategy for break-out growth and performance, leadership in core businesses and to deliver best value to its clients.