Effects of Mortality on Levels of Kinship
Citation: Goldman (1986) Effects of Mortality on Levels of Kinship.
Changes in fertility and mortality indirectly affect intra-family relations, but they directly determine the numbers of kin who are available at any given time to be part of a family, both in terms of the numbers of kin who are born under specified regimes of fertility and mortality and then numbers who remain alive at successive ages. In this article, Goldman uses simulations based on data from the Republic of Korea from 1955-1959 to 1975-1979, assuming a stable population, to determine the average numbers of female descendants and collateral kin ever born and still alive for women of various ages to investigate the relationship between fertility and mortality schedules. By and large, the changes in eventual numbers of kin in the period reflect the decline in Korean fertility more than the rise in life expectancy. Not surprisingly, large reductions in fertility from 1955-1959 to 1975-1979 result in large decreases in the number of daughters, sisters, nieces, aunts, and cousins who are ever born. The decline in numbers of daughters embodies the drop in the NRR, a decrease of 41%, whereas the decrease in numbers of granddaughters reflects the drop in the NRR2, a decrease of 65%. Average number of sisters ever born also drops over the period, but is little influenced by mortality conditions because Goldman only considers sisters of a living woman. Mortality has a much greater effect on numbers of nieces and cousins ever born, as compared with numbers of sisters and aunts, because the higher mortality risks of infancy and childhood come into play (which sisters and aunts already have a surviving sister/niece indicating that a mother/sister survived to give birth to the reference woman). Reductions in death rates raise the chances that each of these types of kin will be alive at a specified age of the reference person. For those kin who are generally as old or older than the woman herself i.e., sisters, cousins, and aunts the changes from 1955-1959 to 1975-1979 in numbers of living kin is notably smaller than the change in numbers of kin ever born. That is, the rise in life expectancy partly offsets the dramatic decline in fertility in terms of numbers of surviving kin. Nevertheless, the "kin-reducing" effect of the fertility decline remains significant. For example, whereas the level of mortality has barely any effect on sisters ever born, the effect on surviving sisters is substantial, at both a high and a low level of fertility. By age 50, a woman from the high fertility, low life expectancy population (GRR=3, e0=30) has the same number of living sisters as a 50-year-old woman from the low fertility (GRR=1), high life expectancy (e0=70) population. Without the changes in fertility, the contrast between the low and high life expectancy populations would be substantial. The combination of a 50% reduction in fertility and a 10-year increase in life expectancy, as in the Republic of Korea during this period, shows the dominating effects of fertility: i.e., there is a substantial reduction in the numbers of living descendants and collateral kin throughout the life cycle of the reference woman. On the other hand, from the reference woman's point of view, changes in fertility and mortality obviously have no effect on the number of parents, grandparents, and great-grandparents ever born. Declines in mortality, however, can greatly increase the survivorship of these kin. Hence, the net effect of a demographic transition is a reduction in the proportion of the family consisting of collateral kin e.g., sisters and cousins and an increase in the proportion composed of parents, grandparents, and even great-grandparents.