THE FECUNDITY AND FERTILITY OF WOMEN. 



485 



Fecundity. 



Age at Marriage. 





Age 20-24 



Age 25-29 



Age 30-34 



Age 35-39 



Age 40-44 



Age 45-49 



15-19 



















Table . . . 



641 



52-1 



36 2 



196 



24 







3 (43— age) . 



630 



480 



330 



180 



30 





20-24 



















Table . . . 





617 



41-7 



24-5 



11-4 



0-3 





3 (46— age) . 





570 



420 



27'0 



120 



00 



25-29 



















Table . . . 







40-6 



282 



91 



13 





2 '6 6 (47-5— age) 







41-4 



280 



14-7 



1-4 



30-34 



















Table . . . 









340 



192 



4-5 





3 (48-5— age) . 









345 



195 



4-5 



These formulae seem to represent the tables pretty closely — with the exception 

 of a solitary number for those married at 25-29 — and if they may be trusted, 

 indicate a very curious result. Of course, when the fecundity is given by an 

 expression of the form k (C — i), C is the age at which sterility arrives. 



Now, it appears that we have for wives married at 



15-19 

 20-24 

 25-29 

 30-34 



Fecundity. 

 k (43— age) 

 k (46 — age) 

 k (47 - 5— age) 

 k (48-5— age) 



In words, the advent of sterility is hastened by early marriage. 

 Thus sterility occurs according to the following table :— 



Age at Marriage. 

 15-19 

 20-24 

 25-29 

 30-34 



Age of Sterility. 

 43 

 46 

 47-5 

 48-5 



This is singular enough, and seems to be well borne out by the tables, since 

 the age of sterility is uniformly later as the age of marriage is greater. But, of 

 course, far more extensive observations must be made and discussed before such 

 a point as this can be settled. 



Accepting it, however, for the present, we may calculate from the last table, 



and the table of fecundity already given, the whole fertility as depending on the 



age at marriage. For, if t be the age at marriage, C t the corresponding age of 



sterility — 



Whole fertility = \ h (C t - *) 2 . 



In this formula k is to be found. But we have 



VOL. XXIV. PART II. 



Fecundity at marriage =/t = k (C t — t). 

 Hence, whole fertility = \f t (Ct — t). 



6p 



