The real nature of insurance is often confused. The word "insurance" is sometimes applied to a fund that is accumulated to meet uncertain losses. For example, a specialty shop dealing in seasonal goods must add to its price early in the season to build up a fund to cover the possibility of loss at the end of the season when the price must be reduced to clear the market. Similarly, life insurance quotes () take into consideration the price the policy would cost after collecting premiums from other policyholders.

This method of meeting a risk is not insurance. It takes more than the mere accumulation of funds to meet uncertain losses to constitute insurance. A transfer of risk is sometimes spoken of as insurance. A store that sells television sets promises to service the set for one year free of charge and to replace the picture tube should the glories of television prove too much for its delicate wiring. The salesman may refer to this agreement as an "insurance policy." It is true that it does represent a transfer of risk, but it is not insurance.

An adequate definition of insurance must include both the building-up of a fund or the transference of risk and a combination of a large number of separate, independent exposures to loss. Only then is there true insurance. Insurance may be defined as a social device for reducing risk by combining a sufficient number of exposure units to make the loss predictable.

The predictable loss is then shared proportionately by all those in the combination. Not only is uncertainty reduced, but losses are shared. These are the important essentials of insurance. One man who owns 10,000 small dwellings, widely scattered, is in almost the same position from the standpoint of insurance as an insurance company with 10,000 policyholders who each own a small dwelling.

The former case may be a subject for self-insurance, whereas the latter represents commercial insurance. From the point of view of the individual insured, insurance is a device that makes it possible for him to substitute a small, definite loss for a large but uncertain loss under an arrangement whereby the fortunate many who escape loss will help to compensate the unfortunate few who suffer loss.

The Law of Large Numbers

To repeat, insurance reduces risk. Paying a premium on a home owners insurance () policy will reduce the chance that an individual will lose their home. At first glance, it may seem strange that a combination of individual risks would result in the reduction of risk. The principle that explains this phenomenon is called in mathematics the "law of large numbers." It is sometimes loosely referred to as the "law of averages" or the "law of probability." Actually, it is but one portion of the subject of probability. The latter is not a law at all but merely a branch of mathematics.

In the seventeenth century, European mathematicians were constructing crude mortality tables. From these investigations, they discovered that the percentage of males and females among each year's births tended everywhere toward a certain constant if sufficient numbers of births were tabulated. In the nineteenth century, Simeon Denis Poisson gave to this principle the name "law of large numbers."

This law is based on the regularity of the occurrence of events, so that what seems random occurrence in the individual happening simply seems so because of insufficient or incomplete knowledge of what is expected to occur. For all practical purposes the law of large numbers may be stated as follows:

The greater the number of exposures, the more nearly will the actual results obtained approach the probable result expected with an infinite number of exposures. This means that, if you flip a coin a sufficiently large number of times, the results of your trials will approach one-half heads and one-half tails, the theoretical probability if the coin is flipped an infinite number of times.