The insurance business is based on the spread of risk. The more widely risk is spread, the more accurately loss can be estimated. An insurance company can more accurately estimate the probability of loss on 100,000 homes than on ten. Years ago, insurers were required to use standardized forms and rates developed by rating agencies. Today, large insurers use their own statistical loss data to develop rates. But small insurers, or insurers focusing on special lines of business, with insufficiently broad loss data to make them actuarially reliable depend on pooled industry data collected by such organizations as the Insurance Services Office (ISO) which provides information to help develop rates such as estimates of future losses and loss adjustment expenses like legal defense costs.

"Rating Bureau" In Context

"SAN FRANCISCO—California insurers filed workers compensation manual rates that rose 4% on average during the last six months of 2011, according to information released Tuesday by the Workers’ Compensation Insurance Rating Bureau of California."