Catastrophes have cut sharply into the bottom lines of US reinsurers, according to the Reinsurance Association of America.

Fifteen out of the 19 property and casualty reinsurers surveyed reported net underwriting losses for the first nine months of this year.

Average combined ratios blew out to an unprofitable 108.8% compared with 96.6% in the nine months to September 30 last year.

Berkshire Hathaway, a major reinsurance company owner, experienced mixed results. Berkshire’s National Indemnity posted the largest net underwriting loss of $US840 million ($821.23 million), but Gen Re posted a gain of $US44.9 million ($43.89 million).

Where there were profits they were meagre: Swiss Re America reported net underwriting gains of $US71.7 million ($70.09 million), Toa Re America posted nearly $4 million ($3.91 million) and Scor US /Scor Re recorded a mere $US255,000 ($249,298).

Munich Re posted a US net underwriting loss of $US263.5 million ($257.61 million); Odyssey Re $US224.2 million ($219.18 million); and Transatlantic/Putnam Re $US429.6 million ($419.22 million).

Overall, the net value of premiums written during the nine-month period increased 12.2% to $US20.54 billion ($20.08 billion) and policyholder surplus fell to $US104.9 billion ($102.55 billion) from $US107.5 billion ($105.09 billion).