In the United Kingdom the customary approach to non-life insurance has been to rely more on the practical experience and flair of the underwriter than on a statistical examination of the experience. In some branches of non-life insurance an office is able to make adequate adjustments to its rates on the basis of claim ratios (i.e. the amounts of claims divided by the premiums) for fairly broad groups. In the more competitive branches such as motor insurance the experience needs to be examined in much greater detail, not merely to satisfy the minimum requirement of guarding against selection of the better risks by other insurers, but more positively in order to find out the extent to which the risk varies with each of the existing rating factors and any possible alternatives. Also, because of the rapidity with which conditions are liable to change, the experience studied must be as up to date as possible if reasonably reliable estimates of the future are to be made.