548 HUMAN BIOLOGY 



occupied males of the same ages. The single cross-hatched 

 column is shorter, in every one of these first occupational 

 groups, than is the solid column. Similarly in these same six 

 occupational groups the number of children ever born in 

 each group forms a still smaller percentage of the total 

 number of children, than do either the males forty-five 

 years and over or the more fertile families in each group of 

 their respective columns. The double cross-hatched columns 

 in these six occupational classes are shorter than either the 

 solid or the single-hatched columns. These results mean that 

 the men aged forty-five and over in these occupational 

 classes have not contributed to the next generation in as high 

 a proportion as their own representation in this generation. 



The case is quite difi"erent for the last three occupational 

 groups {Manufacturing, Agriculture, and Extraction of 

 minerals). In these three groups the percentage of children 

 ever born, and the percentage of more fertile families is 

 higher than the percentage of males forty-five years of age 

 and over in the total population of occupied males. In each 

 of these three occupational groups the double cross-hatched 

 column is taller than the single cross-hatched columns, 

 which in turn is taller than the solid column. The men aged 

 forty-five and over in these three occupational classes have 

 contributed to the next generation more than their own 

 proportionate representation in this generation. The excess 

 contribution is particularly marked in the case of the 

 farmers. 



Summing the whole case up it appears that the great 

 laboring groups. Manufacturing, Agriculture and Mining, 

 not only have a higher proportion of more fertile famihes per 

 unit of population so occupied, than do the other occupa- 

 tional! groups, but also they have a much larger average 

 number of children per family. Put in another way it comes 

 to this; In our population it appears that the Professional, 

 Clerical, Trade, Domestic and personal service. Public 

 service, and Transportation occupational classes are reproduc- 

 ing themselves in such a manner as not to maintain in quite 

 its present status their relative representation in the popula- 

 tion. But the heavy laboring classes. Manufacturing, 

 Agriculture, and Mining, are reproducing themselves in 



