Catastrophe reinsurance rates for Japanese insurers rose by up to 50% at April 1 renewals after last month's earthquake and tsunami, but renewals for some noncatastrophe exposures were relatively stable despite the continuing chaos in Japan, reinsurance brokers say.

As a result of the uncertainty generated by the crisis, mutual insurers in Japan elected to extend their existing contracts rather than negotiate a formal renewal.

After the March 11 earthquake and tsunami in the country's northeast region flattened buildings, caused fires, disrupted business and damaged a nuclear power plant, insurers continue to scramble to assess losses. Insurers in Japan usually exclude nuclear-related damages, and a government-backed program there buffers insurers from residential earthquake risk, experts say.

Japanese insurers traditionally renew their reinsurance protections on April 1, but this year most mutual insurance companies extended their existing agreements with reinsurers for up to three months, according to Willis Re, the reinsurance broking arm of London-based Willis Group Holdings P.L.C.

But more than 10 nonlife insurers kept their April 1 renewals, and rates on some coverage for property damages related to earthquakes rose between 20% and 50% compared with 2010.

For other risks, reinsurance rates changed little. For example, Guy Carpenter & Co. L.L.C., the reinsurance broking arm of New York-based Marsh & McLennan Cos. Inc., said in a report that fire reinsurance treaties, which exclude Japanese earthquake risks “generally enjoyed a smooth and stable renewal” with stable pricing.

“The market is still orderly,” said James Vickers, chairman at Willis Re International & Specialty in London. “Outside of natural catastrophe-exposed business, it's not yet enough to make everybody think, "I have to increase my rates on all lines.'”

A spokeswoman for German reinsurer Munich Reinsurance Co. declined in an email to give an overview of pricing, saying the renewal process is still ongoing. “However, according to our past experience, reinsurance price levels increase in times of high uncertainty and after large catastrophe events,” she said.

A spokesperson for MS&AD Insurance Group Holdings Inc. in Japan said the company faced reinsurers' increasing pressure to raise rates during renewal negotiations. MS&AD renewed its catastrophe treaty “in relatively successful condition,” the spokesperson said in an email.

David Flandro, global head of business intelligence at Guy Carpenter, said in a statement that the earthquake's timing slowed the process of quoting prices on reinsurance contracts.

Guy Carpenter and Willis Re noted that many reinsurers have exhausted their annual catastrophe loss budgets for the year, after experiencing the Japanese earthquake in addition to events ranging from floods in Australia to political unrest in the Middle East.

“As a general understanding, this earthquake...will certainly affect the reinsurance market,” said Takashi Okuma, general manager in the International Department at The General Insurance Assn. of Japan, in an email.