| Under 20 years | 8.8% |
| From 20 to 25 years | 25.4% |
| From 25 to 30 years | 29.4% |
| From 30 to 35 years | 21.6% |
| From 35 to 40 years | 11.5% |
| Over 40 years | 3.3% |
In these cases the maximum fertility was obtained at the age of 27.
The physiological fertility of women is much more clearly manifested when we compare the fertility of women who have been married a few years only, with the fertility of women in the later years of married life. In the earlier period, the effective fertility more nearly approaches the physiological fertility, because at this time the various influences by means of which fertility is later so greatly diminished have not yet come into operation. In this connection the following data, published by Körösi, regarding the percentage fertility of recently married women, and that of married women in general, will be found of interest:
| Recently-married women. | All married women. | |
|---|---|---|
| At ages 20 to 35 years. | 32.9% | 20.6% |
| At ages 35 to 40 years. | 32.7% | 14.7% |
| At ages 40 to 45 years. | 21.4% | 5.9% |
Inasmuch as we learn from this table that in the case of women aged 40 and upward, the newly married exhibit a fertility of four times as great as that of married women in general, in whom pregnancy has already become rare, we can infer the influence upon fertility of abstinence and of artificial measures for the prevention of conception.
On the average, the maximum fertility of woman, that is, the maximum of effective fertility, is attained at the age of 18 to 20 years. Extreme youthfulness, and also the opposite condition, too advanced an age, when marriage is entered on, impair a woman’s fertility; whereas the conditions most favourable to fertility are that, at the time of marriage, the uterus should have attained its fullest development, and the ovaries also should be completely mature; this is not usually the case at puberty, but rather at the age of 20, 21, or 22 years. In Austria-Hungary, of 100 marriages in which the wife’s age at marriage was less than 18 years, the average offspring in the course of a single year were 36 to 38 children; in the case of 100 marriages in which the wife’s age at marriage was 18 to 20 years, the average offspring in a year were 40; this being the maximum fertility, the number of offspring in a year per hundred marriages (i. e., the percentage fertility), now undergoes a regular decline as the wife’s age at marriage increases; at an age of 25, the percentage fertility is 32; at the age of 30 years, the fertility is 24%; at the age of 35, 17%; at the age of 40 years barely 10%; at the age of 45, 7%; at ages 45 to 50, 0.1%. Thus, from the last figure, we see that of a thousand women marrying at the age of 50 years, one only gives birth to a child. Men obtain their maximum fertility (i. e., procreative capacity) at the age of 25 or 26 years; at this age their fertility amounts to 35% (that is, of 100 marriages at this age, 35 children will on the average be born within a single year); at the age of 35 years, the percentage fertility of men falls to 23; at the age of 45 years, it is 9½%; at 55, 2.2%; at 65, ½% (Körösi-Blaschko).
Whereas hitherto we have considered only the monogenous fertility of married women, we must remember that the figures relating to their biogenous fertility are also of interest—that is to say, the changes which a woman’s fertility experiences in married life in respect of the peculiarities of her husband; and of these peculiarities, the easiest to make the object of statistical investigation is the husband’s age. The age of the husband exercises an important influence upon the fertility of the wife, as is proved by the following figures published by Körösi:
| Age of the Father. | Age of the Mother. | ||
|---|---|---|---|
| 25 years. | 30 years. | 35 years. | |
| 25 to 30 years | 35.6% | 25.0% | 21.2% |
| 30 to 35 years | 31.2% | 23.6% | 19.9% |
| 35 to 40 years | 27.5% | 21.8% | 19.4% |
| 40 to 45 years | 16.7% | 14.0% | |
| 45 to 50 years | 14.4% | 10.9% | |
| 50 to 55 years | 10.9% | ||
Also:
| Age of the Mother. | Age of the Father. | |||
|---|---|---|---|---|
| 25 years. | 35 years. | 45 years. | 55 years. | |
| Under 20 years | 49.1% | |||
| 20 to 25 years | 43.0% | 31.3% | 16.0% | |
| 25 to 30 years | 30.8% | 27.3% | 18.5% | |
| 30 to 35 years | 33.5% | 23.7% | 14.4% | 8.1% |
| 35 to 40 years | 18.9% | 11.8% | 6.7% | |
| 40 to 45 years | 6.6% | 6.1% | 3.0% | |