14. Effect of differential mortality on population sex ratio

In view of the development which has been markedly more favourable for the survival of females than males (and not only at old age), one would expect a commensurate and sustained increase. in the proportion of women in old age populations as well. While such an increase has certainly taken place, it has not been entirely universal and has largely come to a stop or even turned into a decrease in the 1980s.

        Figure 11 shows the development of the sex ratio among the oldest-old population in 28 countries. Because of the lopsided relation in favour of women, it was found more illuminative to invert the usual sex ratio and give the number of women per men.

        In five countries (Iceland, Japan, Poland, Portugal and Spain) the sex ratio did not change much during the period observed. In the other 23, the ratio of females per male increased rapidly during most of the period and the excess of females over males doubled or tripled in many cases. In the 1980s, however, a drastic change took place: in 8 countries (including England & Wales, France and Australia), the ratio turned decisively down while in 6 others it stopped growing. It continu~d to increase in 9 countries but in some of them at slower speed.

        The explanation of the paradox of a growing proportion of men in the population while the mortality of women was declining faster, lies not in the death rates but in the numbers of lives saved. Because male mortality is higher than the female, a proportionate decline in both and even a somewhat smaller decline in the former, results in the saving of more male than female lives. As these are cumulated age by age, the number of men reaching an advanced ag will grow relatively faster than that of women reaching the same age. Fluctuations in sex ratio are also caused by the succession of male cohorts, some of which have suffered war losses and others not.

        Another way to understand the process is to consider that more boys are born than girls, the excess being about 5 percent. In the past, this excess was wiped out in a few years so that at the latest when the cohort reached marriageable age, the numbers of both sexes were equal, and after that, women outnumbered men. This is no longer happening. Premature mortality is in developed countries now so low that although it still is higher for males than females, parity in numbers is reached only around age 50 or even later. Consequently, among those reaching an advanced age, the proportion of males has begun to increase. In numerous countries of the database this has happened in the 1980s to persons reaching age 80. The same, however, is not yet happening to those reaching age 90 or 100.

Updated by V. Castanova, 1 March 1999