Experts have a very hard time estimating or judging exactly how the population will grow and when. It isn’t because their figures are that far off; it is mainly because of people. Humans are not very predictable when it comes to having children. Experts missed the postwar baby boom in the United States because they could not predict how people would act. When people want to have children they do, no matter what the outside influences are. The trend for the past decade has been much more of how couples perceive their own welfare rather than to any social stigma or religious affiliation.
Population experts use fertility rates to determine population size. A fertility rate is the number of live births per 1,000 women in the reproductive age group (15 to 44 in the United States and up to 49 years in many other countries). For further projections demographers use the total fertility rate, which is a projection of the average number of children a woman will have during her entire reproductive period. The crude birth rate reached a record low in 1968 because a smaller proportion of the total population were women in the 15-44 age group in the late 1960’s than in 1936. In 1936, 24% of the population consisted of women in those childbearing years; in 1967, only 20%. In 1967 there were an estimated 40.2 million women in the 15 40 age class. By 1970 the U.S. Census Bureau estimated that there were about 42.3 million women in this class. In 1975 the number of women of childbearing age was projected to be about 46.9 million, an increase of 17% over 1967. And we will have to wait and see what the 1980’s census has to say about the percentage of women in the childbearing years. Do you think it will be a lot higher than in 1975?