In their text book, The Practice of Life Assurance, published in 1952, Coe and Ogborn devoted less than four pages to the methods of calculating premiums for varying temporary assurances, including family income policies. At that time decreasing temporary assurances were relatively uncommon except for a block of single-premium policies transacted mainly by a small number of offices which specialized in them.

Since that date, however, the transaction of this type of policy on an annual-premium basis has assumed very substantial proportions, particularly in connexion with mortgages, and the cover provided varies considerably among different offices. Some are prepared to go to considerable lengths to provide exact cover, whereas others appear reluctant to go into any great refinements. This is understandable as the calculation of premium rates is quite a formidable task whichever of the known methods is used. The not infrequent changes in building societies' interest rates add considerably to the difficulties.