The most difficult aspect of the insurance business is the underwriting of policies. Using a wide assortment of data, insurers predict the likelihood that a claim will be made against their policies and price products accordingly. To this end, insurers use actuarial science to quantify the risks they are willing to assume and the premium they will charge to assume them. Data is analyzed to fairly accurately project the rate of future claims based on a given risk. Actuarial science uses statistics and probability to analyze the risks associated with the range of perils covered, and these scientific principles are used to determine an insurer's overall exposure. Upon termination of a given policy, the amount of premium collected and the investment gains thereon minus the amount paid out in claims is the insurer's underwriting profit on that policy. Of course, from the insurer's perspective, some policies are winners (i.e., the insurer pays out less in claims and expenses than it receives in premiums and investment income) and some are losers (i.e., the insurer pays out more in claims and expenses than it receives in premiums and investment income).

An insurer's underwriting performance is measured in its combined ratio. The loss ratio (incurred losses and loss-adjustment expenses divided by net earned premium) is added to the expense ratio (underwriting expenses divided by net premium written) to determine the company's combined ratio. The combined ratio is a reflection of the company's overall underwriting profitability. A combined ratio of less than 100 percent indicates profitability, while anything over 100 indicates a loss.

Insurance companies also earn investment profits on “float”. “Float” or available reserve is the amount of money, at hand at any given moment, that an insurer has collected in insurance premiums but has not been paid out in claims. Insurers start investing insurance premiums as soon as they are collected and continue to earn interest on them until claims are paid out.

In the United States, the underwriting loss of property and casualty insurance companies was $142.3 billion in the five years ending 2003. But overall profit for the same period was $68.4 billion, as the result of float. Some insurance industry insiders, most notably Hank Greenberg, do not believe that it is forever possible to sustain a profit from float without an underwriting profit as well, but this opinion is not universally held. Naturally, the “float” method is difficult to carry out in an economically depressed period. Bear markets do cause insurers to shift away from investments and to toughen up their underwriting standards. So a poor economy generally means high insurance premiums. This tendency to swing between profitable and unprofitable periods over time is commonly known as the "underwriting" or "insurance" cycle.

Property and casualty insurers currently make the most money from their auto insurance line of business. Generally better statistics are available on auto losses and underwriting on this line of business has benefited greatly from advances in computing. Additionally, property losses in the US, due to natural catastrophes, have exacerbated this trend.

Finally, claims and loss handling is the materialized utility of insurance. In managing the claims-handling function, insurers seek to balance the elements of customer satisfaction, administrative handling expenses, and claims overpayment leakages. As part of this balancing act, insurance fraud is a major business risk that must be managed and overcome.

Reference: www.wikipedia.org