Mortality Decline in the 20th Century and Supply of Kin Over the Life Course
Declining mortality over the 20th century has altered the supply of older relatives in the kin networks of persons at all stages of life. Mortality decline has also changed the supply of kin for older persons. Using period life tables for every 20 years from 1900 to 2000, Uhlenberg calculated the proportion of person who, at various stages of the life course, would have grandparents, parents, spouses, siblings and children still living.
Uhlenberg simulates family composition by imposing rules of marriage and fertility (assuming there is one son and one daughter only) and the mortality conditions at the time and then looks at the resulting numbers of kin alive. Uhlenberg finds that the supply of grandparents has changed dramatically over time. Under his assumptions, mortality levels existing in 1900 imply that fewer than ? of all children began life with all 4 of their grandparents alive, and by age 30 only 21% had any surviving grandparent. By the end of the century, on the other hand, over 2/3 will have begun life with all grandparents still living and more than ? will still have at least one grandparent alive when they reached age 30. Mortality declines in the last 40 years have been especially important in increasing the supply of grandparents for persons in the post-childhood years of life. Regarding survival of older parents, the probability of having both parents alive at age 40, 50, and 60 has increased since 1900. Moreover, individuals are more likely to have a mother alive at older ages with as many as 6.5% having only a mother alive at age 70 in 2000 as compared with 1.6 in 1960 and less than 1% from 1900 to 1940. Less than 1% can expect to have only a father alive from 1900 to 2000. Regarding survival of spouses, under 1900 mortality conditions, only half of men and a third of women who survive to age 70 would still have a living spouse. By 2000, these proportions will increase to 85% and 61%, respectively. However, while decreasing death rates created large gains in potential years that men and women could expect to live in uninterrupted marriages, increasing divorce rates have had an opposite effect. Because of changes in divorce rates and death rates by 2000, the prospect of 70-year-old mean and women still living with a first spouse are quite similar under conditions in 1900 and 2000.
Sibling relationships are unique in their potential longevity. Again, the magnitude in historical change is large. For example, for those who survive to 70 with a sister 3 years younger, in 1900 27% of these individuals would have their sister still living while in 2000, the proportion was 75%. Because of gender differences in declining mortality, differences in the prospects of a sister surviving, compared to a brother, grew much larger between 1920 and 1980. At older ages, where death rates are high, the difference in probability of an older sibling compared to a younger one still being alive are significant.
Today, relatively few children now die before their parents. With low mortality, it is not necessary to hear more children in order to be relatively certain that one will have surviving children when one is old. Over the last century, moreover, it has become increasingly likely that when only 1 child survives, that child is a daughter. For example, women who bear sons at age 25 now are more likely to have those sons alive when they are 80 (87%) than women in 1900 were to have their sons survive the first 2 years of life (82%). And if the child is a daughter, a higher proportion are now still living when their mothers reach age 90 (86%) than were surviving for just 2 years around 1900 (85%).