An office transacting life assurance relies for its results on the law of averages as revealed by investigation into past experience. Statistics are compiled in order that an estimate of future mortality may be obtained, and i f each assurance accepted were for the same amount, the office could, if it wished, retain for its own account all its business. In practice proposals are received for amounts ranging from the smallest sum for which the company will issue a policy up to hundreds of thousands of pounds, and clearly as the bulk of the business is for small sums assured an office might experience violent fluctuations in financial results if it retained the whole of the large proposals, even if the mortality experience were according to expectations and consistent from year to year.