242 
Duration of Life and Number of Offspring 
be prejudicial to longevity at all, it must be only those of exceptional physique 
who have attained the ages of 60 and 75 years, and the more satisfactory method 
of determining the correlation between fertility and longevity would be to take 
into account the deferred expectation beyond those ages by survivors of age 46. 
(It may be remarked that the expectation here referi'ed to is not the actuarial 
expectation of life — but of that hereafter.) This expectation has been calculated 
for mothers of each sized family, and the results are shown in Table IX. 
TABLE IX. 
Average Duration of Life by Mothers Surviving Age 46. 
Number of 
children 
in Family 
Duration beyond 
60 years of age 
Duration beyond 
75 years of age 
Number of 
children 
in Family 
Duration beyond 
60 years of age 
Duration beyond 
75 years of age 
0 
9'53 years 
2-03 
years 
9 
10-03 
years 
2-32 years 
1 
9-61 „ 
2-28 
10 
9-61 
2-06 „ 
2 
10-47 „ 
2-56 
5) 
11 
9-07 
1-65 „ 
3 
10-04 „ 
2-32 
?J 
12 
9-70 
)» 
1-91 „ 
k 
10-49 „ 
2-53 
)5 
13 
9-13 
1-57 „ 
5 
10-57 „ 
2-50 
U 
10-30 
)) 
75 
2-28 „ 
6 
10-56 „ 
2-48 
15 
8-46 
1-09 „ 
7 
9-75 „ 
2-08 
)) 
16 
8-43 
11 
1-41 „ 
8 
10-26 „ 
2-41 
I) 
17 
6-25 
11 
0-96 „ 
These results were obtained by dividing the total life beyond 60 and beyond 
75 years of age by the number of mothers who had survived their forty-sixth 
year and adding a half year for the year of death. Taking advantage of the 
knowledge derived from the parabolas of the preceding investigation that the 
maximum duration of life was about six children, these results were broken up 
at that number and the correlation and regression straight lines were determined 
at each period as from 0 to 6 children and from 6 to 17 children, with the results 
set forth in Tables X. and XI. 
TABLE X. 
General Results. 
Period of Life 
Size of Family 
Mean 
Duration 
of Life 
(years) 
Mean 
Size of 
Family 
Standard 
Deviation 
Correlation. 
Duration of Life 
and Fertility 
Kegression 
Duration 
of Life 
(Unit = l 
year) 
Size 
of 
Family 
After 60 years 
>i )) 
After 45 years 
)) )) 
0 to 6 children 
6 to 17 „ 
Oto 6 „ 
6 to 17 „ 
10-1636 
9-8640 
2 -.3647 
2-1366 
2-9840 
8-9946 
2-9840 
8-9946 
-44058 
-24559 
-19396 
-30305 
2-1561 
2-2957 
2-1561 
2-2957 
+ -89004+ -00194 
- -68479 + -00467 
+ -64963 + -00539 
- -74144+ -00396 
+ -18187 
- -14782 
+ -05844 
- -09788 
