In determining premiums and premium rate structures, insurers consider quantifiable factors, including location, credit scores, gender, occupation, marital status, and education level. However, the use of such factors is often considered to be unfair or unlawfully discriminatory, and the reaction against this practice has in some instances led to political disputes about the ways in which insurers determine premiums and regulatory intervention to limit the factors used.

Large number of similar exposure units: Since insurance operates through pooling resources, the majority of insurance policies are provided for individual members of large classes, allowing insurers to benefit from the law of large numbers in which predicted losses are similar to the actual losses. Exceptions include Lloyd's of London, which is famous for ensuring the life or health of actors, sports figures, and other famous individuals. However, all exposures will have particular differences, which may lead to different premium rates.
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.

The financial stability and strength of an insurance company should be a major consideration when buying an insurance contract. An insurance premium paid currently provides coverage for losses that might arise many years in the future. For that reason, the viability of the insurance carrier is very important. In recent years, a number of insurance companies have become insolvent, leaving their policyholders with no coverage (or coverage only from a government-backed insurance pool or other arrangement with less attractive payouts for losses). A number of independent rating agencies provide information and rate the financial viability of insurance companies.

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Often a commercial insured's liability insurance program consists of several layers. The first layer of insurance generally consists of primary insurance, which provides first dollar indemnity for judgments and settlements up to the limits of liability of the primary policy. Generally, primary insurance is subject to a deductible and obligates the insured to defend the insured against lawsuits, which is normally accomplished by assigning counsel to defend the insured. In many instances, a commercial insured may elect to self-insure. Above the primary insurance or self-insured retention, the insured may have one or more layers of excess insurance to provide coverage additional limits of indemnity protection. There are a variety of types of excess insurance, including "stand-alone" excess policies (policies that contain their own terms, conditions, and exclusions), "follow form" excess insurance (policies that follow the terms of the underlying policy except as specifically provided), and "umbrella" insurance policies (excess insurance that in some circumstances could provide coverage that is broader than the underlying insurance).[36]
Certain insurance products and practices have been described as rent-seeking by critics.[citation needed] That is, some insurance products or practices are useful primarily because of legal benefits, such as reducing taxes, as opposed to providing protection against risks of adverse events. Under United States tax law, for example, most owners of variable annuities and variable life insurance can invest their premium payments in the stock market and defer or eliminate paying any taxes on their investments until withdrawals are made. Sometimes this tax deferral is the only reason people use these products.[citation needed] Another example is the legal infrastructure which allows life insurance to be held in an irrevocable trust which is used to pay an estate tax while the proceeds themselves are immune from the estate tax.

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]
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: