Retrospectively rated insurance is a method of establishing a premium on large commercial accounts. The final premium is based on the insured's actual loss experience during the policy term, sometimes subject to a minimum and maximum premium, with the final premium determined by a formula. Under this plan, the current year's premium is based partially (or wholly) on the current year's losses, although the premium adjustments may take months or years beyond the current year's expiration date. The rating formula is guaranteed in the insurance contract. Formula: retrospective premium = converted loss + basic premium × tax multiplier. Numerous variations of this formula have been developed and are in use.
Insurance companies earn investment profits on "float". Float, or available reserve, is the amount of money on hand at any given moment that an insurer has collected in insurance premiums but has not paid out in claims. Insurers start investing insurance premiums as soon as they are collected and continue to earn interest or other income on them until claims are paid out. The Association of British Insurers (gathering 400 insurance companies and 94% of UK insurance services) has almost 20% of the investments in the London Stock Exchange. In 2007, U.S. industry profits from float totaled $58 billion. In a 2009 letter to investors, Warren Buffett wrote, "we were paid $2.8 billion to hold our float in 2008."
Claims and loss handling is the materialized utility of insurance; it is the actual "product" paid for. Claims may be filed by insureds directly with the insurer or through brokers or agents. The insurer may require that the claim be filed on its own proprietary forms, or may accept claims on a standard industry form, such as those produced by ACORD.
NerdWallet averaged rates for 40-year-old men and women for 20 ZIP codes in each state and Washington, D.C., from the largest insurers, up to 12 in each state. “Good drivers” had no moving violations on record and credit in the “good” tier as reported to each insurer. For the other two driver profiles, we changed the credit tier to “poor” or added one at-fault accident, keeping everything else the same. Sample drivers had the following coverage limits: