Upon termination of a given policy, the amount of premium collected minus the amount paid out in claims is the insurer's underwriting profit on that policy. Underwriting performance is measured by something called the "combined ratio", which is the ratio of expenses/losses to premiums.[25] A combined ratio of less than 100% indicates an underwriting profit, while anything over 100 indicates an underwriting loss. A company with a combined ratio over 100% may nevertheless remain profitable due to investment earnings.
Insurance can influence the probability of losses through moral hazard, insurance fraud, and preventive steps by the insurance company. Insurance scholars have typically used moral hazard to refer to the increased loss due to unintentional carelessness and insurance fraud to refer to increased risk due to intentional carelessness or indifference.[22] Insurers attempt to address carelessness through inspections, policy provisions requiring certain types of maintenance, and possible discounts for loss mitigation efforts. While in theory insurers could encourage investment in loss reduction, some commentators have argued that in practice insurers had historically not aggressively pursued loss control measures—particularly to prevent disaster losses such as hurricanes—because of concerns over rate reductions and legal battles. However, since about 1996 insurers have begun to take a more active role in loss mitigation, such as through building codes.[23]
Insurance involves pooling funds from many insured entities (known as exposures) to pay for the losses that some may incur. The insured entities are therefore protected from risk for a fee, with the fee being dependent upon the frequency and severity of the event occurring. In order to be an insurable risk, the risk insured against must meet certain characteristics. Insurance as a financial intermediary is a commercial enterprise and a major part of the financial services industry, but individual entities can also self-insure through saving money for possible future losses.[15]
At the same time, the first insurance schemes for the underwriting of business ventures became available. By the end of the seventeenth century, London's growing importance as a center for trade was increasing demand for marine insurance. In the late 1680s, Edward Lloyd opened a coffee house, which became the meeting place for parties in the shipping industry wishing to insure cargoes and ships, and those willing to underwrite such ventures. These informal beginnings led to the establishment of the insurance market Lloyd's of London and several related shipping and insurance businesses.[6]

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: