THE SIZE OF AMERICAN FAMILIES. 65 



These figures are from a sufficient number of cases to be substan- 

 tiall}^ reliable. For instance, there is not one chance in a thousand 

 that the Harvard average is 10 per cent, too low. The existence and 

 approximate amount of the decrease in the size of family is thus cer- 

 tain. Its substantial identity in Middlebury, a country college in 

 Vermont with a local attendance, in New York University, a city col- 

 lege, and in Wesleyan University, a strongly sectarian college with an 

 attendance drawn from the northeastern states, makes it probable that 

 it has prevailed throughout the college population of the north Atlan- 

 tic states. It must depend upon some fundamental cause. 



City life and advanced age at marriage are out of question. The 

 former cause would work to a far greater extent upon New York Uni- 

 versity or Harvard gTaduates than upon Middlebury graduates, all of 

 whom come from and most of whom go back to life in small towns. 

 Yet in the statistics there is little difference. An increase in the age 

 at marriage can not have been the cause for the simple reason that 

 such increase, as I have elsewhere shown, amounts onlv to a verv few 

 months. An increase in the age at marriage of the wives of our group 

 of men would be a more efficient cause. I know of no available statis- 

 tics to decide the question, but it would seem extremely unlikely that 

 the age of wives should have increased much when the age of husbands 

 has increased so little. 



The most plausible explanation attributes the change to the custom 

 of conscious restriction of offspring. Greater prudence, higher ideals 

 of education for children, more interest in the health of women, inter- 

 ests of women in affairs outside the home, the increased knowledge of 

 certain fields of physiology and medicine, a decline in the religious 

 sense of the impiety of interference with things in general, the long- 

 ing for freedom from household cares — any or all of these may be 

 assigned as the motive for the restriction. The only other explana- 

 tion which to the present writer seems adequate assigns the decreased 

 productivity of college men to real physiological infertility of the social 

 and perhaps of the racial group to which college men and their wives 

 belong. 



It is possible to do more than speculate about the relative shares 

 of unwillingness and incapacity. The figures themselves tell a plain 

 story to the student who examines them in the light of recent knowl- 

 edge of the variability of physical traits. 



If we tabulate the records by decades so as to show the percentages 

 that families of 2, 3, 4, etc., children were of the total number of 

 families, we can see just how the decrease in the averages has been 

 brought about. Suppose for instance that we had in 1803-1814 and 

 in 1865-1874 the following percentages : 



VOL. LXIII. — 5. 



