SynopsisThe Paper discusses the general problem of appreciation and depreciation, with special reference to the relation between maturing assets and maturing liabilities, and describes a method of calculating the bonus-earning power of different classes of policy. This method is used to test the effect on bonus-earning power of two types of changes in interest rates:–(a)a change, such as that caused by the War Loan conversion of 1932, which takes effect gradually; and(b)a subsequent change, due to a rise in the rate of income tax, which has an immediate effect on the income from existing as well as investments.