Mortality in a population is measured by a number of demographic indices such as the crude death rate, the infant mortality rate, the age-specific death rate or the standardised death rate. Still another more comprehensive method of portraying mortality conditions in a population is by means of a life table. A life table as compared to other mortality indices serves many useful purposes. For measuring longevity of life, projecting current population into the future or estimating incidence of widowhood and orphanhood, a life table is essential. For comparison of expectation of life (or average duration of life) at birth and after birth for various ages of different populations the life table is also commonly used. Besides its utility in demographic problems, still another important use of a life table is made by actuaries in life insurance. The life table is also becoming an important tool of investigation for problems of commerce and industry as it enables one to describe the expectation of life of many nonhuman populations. For detailed discussion of various kinds of life tables and their uses, the reader is advised to refer to any one of many standard reference works [6, Chapters 12 and 13].