The Sept. 11, 2001, terrorist attacks, the worst insured catastrophe in American history, were not costly enough to trigger failures of any U.S. insurance companies, according to a university researchers study.

"There was this major fear that our insurance industry would be wiped out by these acts simply because of the enormous payouts," said John Fitzgerald, a finance and insurance professor at Ball State University in Muncie, Ind., who expects to finalize the study in the coming weeks. "However, the only business failures were actually normal exits from the industry."

While initial estimates of Sept. 11 losses ranged as high as $70 billion in the weeks after the attacks, actual damage payments have amounted to between $30 billion and $35 billion over the past three years, Mr. Fitzgerald noted.

The National Association of Insurance Commissioners (NAIC) had announced plans to assess and monitor the financial solvency of insurers affected by the terrorist attacks in New York City and Washington, D.C. The NAICs concern followed questions of insurer solvency raised by Congressman Michael Oxley, chairman of the United States House of Representative's Financial Services Committee.

The NAIC's review was precautionary because of the unprecedented losses expected. NAIC spokesperson Kris Welschmeyer indicated shortly after the attackes that insurer insolvency was "not a giant concern at all."

In September 2001 insurance industry experts reported their industry has $3.1 trillion in assets and liquid reserves and is normally able to withstand heavy losses, although they admitted the losses from the attacks would easily exceed those suffered in the wake of Hurricane Andrew, a 1992 disaster that cost the insurance industry $15.5 billion.