30 This is illustrated by the specially elaborate statistics of Scotland for 1855;
31 the number of women having children, that is, the fecundity, was higher in the years 15 to 19, than at any subsequent age-period, except 20 to 24, and the fact that the earliest age-group is not absolutely highest is due to the presence of a number of immature women. In New South Wales, Coghlan has shown that
if the average number of children is 3.6, then a woman marrying at 20 may expect to have five children, a woman marrying at 28 three children, at 32 two children, and at 37 one child.
Newsholme and Stevenson, again, conclude that the general law of decline of fertility with advancing age of the mother is shown in various countries, and that in nearly all countries the mothers aged 15 to 20 have the largest number of children; the chief exception is in the case of some northern countries like Norway and Finland, where women develop late, and there it is the mothers of 20 to 25 who have the largest number of children.
The postponement in the age of marriage during recent years is, however, so slight that it can only account for a small part of the decline in the birth-rate; Coghlan calculates that of unborn possible children in New South Wales the loss of only about one-sixth is to be attributed to this cause. In London, however, Heron considers that the recognized connection between a low birth-rate and a high social standing might have been entirely accounted for sixty years ago by postponement of marriage, and that such postponement may still account for 50 per cent of it.