274 
Duration of Marriage and Number of Offspring 
or a mean of 38'4 years nearly 60 per cent, are sterile. Although it is noticeable 
that for marriages contracted under 25 years the average offspring is greater for 
each duration of marriage than those contracted under 20 — except for the duration 
2|- years — yet the percentage of issueless wives is also greater. This I think more 
an apparent than a real physiological fact and is due to the larger proportion of 
Fig. 17. Average Issue and Proportion of Issueless Wives. Average Issue shown by 
Firm Lines. Issueless Wives shown by Broken Lines. 
8 
7 
6 
g 3 
2 
1 
N 
-A 
/ 
/ 
B 
— e 
-~< 
c ( 
y— 
— ( 
5 10 15 20 
Duration of Marriage (Yeari>). 
80 
70 
60 
50 
1J 
5! 
40 
so 
30 
=o 
!3 
20 
"S 
10 
25 
Age at Marriage, Under 25, Lines AA' and aa'. 
25—3.5 „ BB' and 66'. 
35—45 ,, CC and cc'. 
prejudiced marriages in the younger group — and to this is also due the slightly 
larger average offspring in the 2^ years' duration of marriage. Taking the six 
years 1897 to 1902 there were 9490 marriages and 3910 antenuptial conceptions, 
or 41 '2 per cent, of prejudiced marriages in the age group under 20, whilst of the 
26,453 marriages contracted between 20 and 25 there were 7899 antenuptial con- 
ceptions or 29*9 per cent. Nor does this represent the full difference, for some 
women who were aged 19 at marriage, were 20 at the birth of the child and 
consequently were included in the later group. If adjustment be made the result 
will of course intensify the difference. This excess of antenuptial conception in 
the lower age group must amply account for the slightly higher proportion of 
issueless wives in the group under 25, but the fact that the average offspring is 
greater in the latter group than in the former — notwithstanding the greater 
proportion of sterile women — proves conclusively that the maximum fertility — 
initial and continuous — lies somewhere between age at marriage 20 and 25. Of 
course the test of fertility is not in the number of offspring produced during the 
reproductive period — for that will be greatest at the earliest age at marriage — but 
the rapidity with which they are produced. 
A favourite method amongst statisticians and others of comparing birthrates 
(at least amongst those who have been able to comprehend the fallacies in the 
