Reinsurers are in the business of reinsuring insurance companies. At the time of writing, the top reinsurance companies in the world, based on last company figures, are:
1. Münchener Rück
2. Swiss Re
3. Berkshire Hathaway / General Re
4. Hannover Rück
5. SCOR
6. Reinsurance Group of America
7. Transatlantic Re
8. Everest Re
9. Partner Re
10. XL Re
Reinsurance companies will also buy reinsurance from other reinsurers. This is known as retrocession. Reinsurance between reinsurers can go back and forth for some time, known as "spiral", until the original reinsurer regains some of their own business. This can, and has in the past affected the insurance industry in a negative way when too many spirals are present in the market.