Survivorship of sons under conditions of improving mortality

The strong desire of fathers to be assured that at least one son will outlive them, coupled with the traditional belief in a high probability of sons predeceasing their father, is often a deterrent to restriction of family size. A calculation of the probabilities of survivorship of sons on the basis of the United Nations Model Life Tables, however, shows that the probabilities of a father being outlived by even one son are remarkably high, particularly after that son has survived the first two years of life. When cohort tables are used, reflecting expected mortality improvements, the probabilities are even higher. In general, it is found that the probability that a two-year-old son will outlive his father is 80% or better, subject to the current mortality level and the age of the father.Finally, this paper examines (1) probabilities of a father being outlived by at least one of two or three sons, (2) probabilities of a mother or of both parents being outlived by a son, and (3) the probability that at least one of two sons will outlive a father when allowance is made for the fact that mortality probabilities of the sons are not independent of one another.