The report says prices for coverage have declined since TRIA was enacted, and take-up rates have improved and are roughly stable at 60% of the aggregate insurance market. This compares, the report says, to 27% in 2003, the first full year TRIA was in effect.

The report specifically says, "In the absence of TRIA, terrorism risk insurance likely would be less available." It adds, "Coverage that would be available likely would be more costly and/or limited in scope."

The report says insurers have "exhibited reluctance" to offer coverage for terrorism risk if the associated losses cannot be predicted and may be unlimited. It says the current law limits an insurer's exposure by sharing the risk of insured losses that could exceed the insurer deductible and capping the aggregate liability of insurers and the federal government at $100 billion. 

Workers' comp insurance "often receives special attention in discussion of terrorism risk insurance" because, by state law, the coverage cannot exclude losses resulting from acts of terrorism, including Nuclear, Biological, Chemical and Radiation (NCBR), according to the report. It notes a January Marsh report stating that, in light of the pending expiration of TRIA, insurers have begun endorsing workers' compensation renewals to advise policyholders that the premium may change Dec. 31, "and that some insurers are setting policy expirations at that date."