RATIOS OF CHILDREN TO WOMEN COMPARED WITH REPLACEMENT NEEDS
The simplest and most obvious measurement of the natural increase or decrease of a population is found in the relation of the crude birth rates and death rates. It is clear that as long as the birth rate exceeds the death rate there is some increase. But with a steadily falling birth rate, the actual rates for births and deaths do not tell a wholly truthful tale or, at least, one easy of correct interpretation. Especially is this true if one desires to arrive at a sound judgment of what the tendencies of the growth of our numbers will be during the next three or four decades.
It is a matter of common knowledge that young children die in rather large numbers, especially during the first year of life. A rate of 7 per cent or 8 per cent for children under 1 year is a low rate. In 1925 out of each 1,000 white children born, 68.3 died before they reached the end of the first year. It is also well known that older people, those above 50, let us say, die in larger numbers than those 10 to 50. The exact rate in 1920 for white males 52 years of age was 13.83 per 1,000. The fact is that from about 12 years of age, when the death rate is lowest (2.20 per 1,000), it rises without interruption. At 42 it is 8.65 per 1,000, almost four times as great as at 12; at 52 it is about 60 per cent greater than at 42; at 62 (28.35 per 1,000), it is over twice as large as at 52; and at 72 (65.41 per 1,000), it is well over twice as large as at 62.1 It is clear, then, that any population in which a large part of the people are under 40 will have a lower crude death rate, other things being equal, than a population with relatively more people over 40.
As is well known, women over 35 contribute comparatively few children to the population (slightly less than 20 per cent of all children according to Dublin's calculations).2 We have shown that the fertility of women married after 17 years of age falls off rapidly. (See Chap. VI, p. 110.) It follows, then, that any population which has been increasing rather rapidly from an excess of births or by immigration must have a relatively young population in which deaths will be few and births many as compared with a more stable population.____________________