When it comes down to the country that can lay claim to the largest group of insurers, the United States isn't atop the list. A.M. Best released its annual rankings of the top 25 global insurers—both by total assets and net written premiums—and while America is well represented on both lists, it's behind Japan an other European insurers in both categories.

The world's largest insurer, measured by assets, is Japan Post Insurance Co., which reported 2009 year-end assets of $1.1 trillion, A.M. Best found. Japan Post is also the fourth-largest insurer worldwide based on net written premiums, at $81 billion for the same year. When looking at net premiums, the world's largest insurer is France-based Axa S.A., with $116,475,691.

European took up more than half (13) of the list when ranked by assets, while Asia and North America each had six.  Among the list of largest insurers ranked by net premiums, North America and Europe each had nine, while Asia had seven.

The statistics show that life insurers tend to dominate the list of insurers ranked by assets, while non-life insurers make up a larger share of the list of insurers ranked by net premiums written.

A.M. Best says the list is based on 2009 financial results because insurers have different filing requirements and deadlines throughout the world. The results also were adjusted for differences in currency and reporting.

World’s Largest Insurers Ranked by Assets

1. Japan Post Insurance Co. Ltd. (Japan)

2. Axa S.A. (France)

3. American International Group Inc. (United States)

4. Allianz SE (Germany)

5. Assicurazioni Generali SpA (Italy)

6. Aviva plc (United Kingdom)

7. MetLife Inc. (United States)

8. Prudential Financial Inc. (United States)

9. Legal & General Group plc (United Kingdom)

10. Nippon Life Insurance Co. (Japan)

11. National Mut Ins Fed Agricultural Coop (Japan) 

12. CNP Assurances (France) 

13. Aegon NV (Netherlands) 

14. Manulife Financial Corp. (Canada) 

15. ING Groep NV (Netherlands) 

16. Zurich Financial Services Ltd. (Switzerland) 

17. Prudential plc (United Kingdom) 

18. Munich Reinsurance Co. (Germany) 

19. Dai-ichi Life Insurance Co. (Japan) 

20. Hartford Financial Services Group Inc. (United States)

21. Predica-Prevoyance Dialogue du Credit (France)

22. Berkshire Hathaway Inc. (United States) 

23. Meiji Yasuda Life Insurance Co. (Japan) 

24. Standard Life Plc (United Kingdom)

25. Sumitomo Life Insurance Co. (Japan)


World’s Largest Insurers Ranked by Net Written Premiums

1. Axa S.A. (France)

2. Assicurazioni Generali SpA (Italy)

3. Allianz SE (Germany)

4. Japan Post Insurance Co. Ltd. (Japan)

5. UnitedHealth Group (United States)

6. American International Group Inc. (United States)

7. National Mutual Insurance Federation of Agricultural Cooperatives (Japan)

8. Munich Reinsurance Co. (Germany)

9. WellPoint Inc. (United States)

10. State Farm Group (United States)

11. Nippon Life Insurance Co. (Japan) 

12. Aviva plc (United Kingdom)

13. Zurich Financial Services Ltd. (Switzerland) 

14. Kaiser Foundation Group of Health Plans (United States)

15. CNP Assurances (France)

16. China Life Insurance (Group) Co. (China)

17. ING Groep NV (Netherlands)

18. Dai-ichi Life Insurance Co. (Japan)

19. Prudential plc (United Kingdom) 

20. Life Insurance Corporation of India (India) 

21. Aetna Inc. (United States)

22. Humana Inc. (United States)

23. Tokio Marine Holdings Inc. (Japan)

24. Allstate Corp. (United States)

25. Berkshire Hathaway Inc. (United States)