NU Online News Service, Jan. 6, 10:27 a.m. EST

A Japanese company tops the list of the world’s largest insurers measured by assets, and by net written premiums, a French insurer comes in first.

According to A.M. Best Co., Japan Post Insurance Company Ltd. had $1.1 trillion in assets at the end of 2009, about a 5.3 percent decline from the prior year but still good enough to eclipse France’s Axa S.A., which had about $962.8 billion.

Japan leads the list of nations with the largest insurers based on assets with six. The United States has five companies on the list, A.M. Best said.

Axa is the world’s largest insurer based on net premiums, with nearly $116.5 billion. Japan Post also appears on this list at the fourth spot with about $81 billion–more than doubling its net written premiums from the prior year.

Life insurers dominate the list based on assets, and non-life companies make up a larger share of the list based on net premiums, A.M. Best said. The United States is represented the most on the list based on net premiums written with nine companies.

American International Group (AIG) is the first U.S.-based insurer to appear on either list, coming in third on the list of assets with about $847.6 billion, a 1.5 percent decline.

AIG ranks sixth on the list of insurers based on net premiums, with about $62.2 billion, according to A.M. Best. The total represents an 18.75 percent decline from the prior year.

UnitedHealth Group is the first U.S. insurer to get on this list, ranking fifth with about $79.3 billion in net premiums.

State Farm Group rounds out the top 10 world’s largest insurers based on net premiums written with about $54 billion, one spot behind WellPoint with about $55.5 billion.

MetLife and Prudential Financial rank seventh and eighth on the list based on assets with about $539.3 billion and $480.2 billion, respectively.

Berkshire Hathaway appears on both lists. Warren Buffett’s company is 22nd based on assets with about $297.1 billion and 25th based on net written premiums with about $27.9 billion, a spot behind Allstate Corp. with about $27.9 billion in net premiums written.

A.M. Best said the ranking would likely change in future editions because of restructuring and competition. AIG sold its life unit Alico to MetLife last year. The sale of AIG Star Life Insurance Company and AIG Edison Life Insurance Company to Prudential Financial should close early in 2011.