Just as the Soviet birth rate has declined since the great industrial push in the early thirties, so the United States has shown a steady decline from the 1970's to the late 1930's. Decreasing child mortality has played a major role. For example, figures reveal that the interval between births when a child lives is substantially greater than when the child dies at birth: breast nursing causes sterility for 11 months, while death at birth causes only two months of sterility.
The second factor common to both countries is the shift from dependence on the family as a source of support in old age to a reliance on support from the government. It used to be that the more children parents had, the more assistance they would receive when they could no longer support themselves. Today, measures like social security, which are part of modern industrialization, make family dependence unnecessary.
In his second project, Heer is making a statistical analysis of the social factors which differentiate fertility of nations. He has approached the problem of the effects of economic development on fertility in a unique way. Although experts have always known that economic development means a lower birth-rate, Heer claims the direct result of economic development is an increase in fertility. An example is the large increase in the American birth rate in the prosperous post World War II period.
It is only the indirect effects of development according to Heer which lead to an eventual depressing of the birth rate. Heer points to the increased cost of children in an industrial urban society where parents have to pay for the space children take up and the food they eat. In an agricultural society children may be used productively in the farm work, and there is no crucial space problem.
Other indirect effects of development are reduced child mortality, perhaps the most important single factor, and increased literacy. The latter is usually accompanied by delayed marriage and a more sensitive sophistication which leads to greater acceptance of family planning. Heer thinks that another indirect result of economic development, increasing technology, caused an eight per cent decrease in the U.S. birth rate over the last year with the acceptance of oral contraceptives.
Heer is also beginning a third survey to determine the effects which reducing mortality will have on the population rate. The study centers on determining how many offspring a couple will need to assure themselves a 95 per cent certainly of one surviving son when the father has reached his 65th birthday. Using a computer, the probability of having one surviving son will be determined at 24 levels of mortality, ranging from average life expectancies of 20 years to 73.9 years. The study assumes no couple can produce more than 12 children. Preliminary results reveal that population growth is greatest in the middle range of mortality. In periods of high mortality, couples will certainly produce many children, but most will not produce as many as they need to assume the survival of at least one son.
In societies where the mortality is so high that a couple must produce seven to nine sons to insure one surviving, the population growth will not achieve its maximum because the limit of children per family is 12. This also means that contraception would be useless in societies at this level, for mothers would try to have as many children as possible.
The population growth peaks at middle mortality where only five or six sons are needed. At this point, the couple would be producing close to the maximum number of children and the ratio of birth rate to death rate will be highest at this level.
The preliminary results of the study are revolutionary because they indicate that contraception cannot curb the population rate in societies with high mortality, and that it becomes really effective only in societies of very low mortality. Thus Heer concludes that "progress in curbing the population explosion may best be brought about through further reduction in mortality," rather than increased contraception.
Still, birth control is being studies in detail in both its ethical and biological aspects, by other members of the Center. Assistant professors Ralph B. Potter and Arthur J. Dyck, both of the Divinity School, teach and do research on the relationship between ethics and population control. Dyck justifies the inclusion of ethics in population studies by pointing out that the real problem in controlling birth rates is not the acceptance of birth control techniques. This often results only in a more even spacing out of a large family, he explained. The real variable is whether people want a large or small family or, as Dyck put it "what one wants out of a family." At this level, the influ-