SOME ASPECTS OF THE BIOLOGY OF HUMAN POPULATIONS 545 



that for each of these variables the condition in the Pro- 

 fessional class is taken as i .0. 



Broadly what Figure 10 shows is that: 



I. For each male forty-five years or over in the class 

 Projessional service in 1920, there was 0.34 of a male of 

 corresponding age in Clerical occupations; 1.60 in Trade; 

 0.47 in Domestic and personal service; 0.23 in Public service; 

 and 0,79 in Transportation. In these six occupational classes 

 more fertile families, as defined above, occurred in about 

 the same proportions relative to the Projessional service 

 class taken as i.oo in both instances, as the dash hne of 

 Figure 10 shows. This means that in these six occupational 

 groups more fertile famihes are represented in about the 

 same relative proportions to each other, as occupied males 

 of corresponding age in the classes as a whole. This is only 

 approximately true, because the population figures are 

 for 1920, and those for more fertile famihes are for 1923. 

 But the general consonance of the relative figures for the 

 six classes named will probably not be significantly disturbed 

 by this consideration. 



2. For every male forty-five or over engaged in Pro- 

 fessional service in 1920, there were 3.22 workers of cor- 

 responding age in Manufacturing and mechanical industries; 

 3.04 in Agriculture; and 0.27 in Extraction of minerals. 

 But for every more fertile family, as here defined, in the 

 Projessional service class, there were 5.64 such famihes in the 

 Manufacturing class; 7.18 in the Agriculture class; and 0.71 

 in the Extraction oj minerals class. What these results 

 mean is that famihes of more than average total fertihty 

 occurred in these three classes, in proportion to the male 

 population of corresponding age, taking the Projessional 

 class as i.oo, from two to three times as often as they did 

 in any of the six occupational classes discussed above. 



3. The relative total number of children ever born, up to 

 and including 1923, in the more fertile famihes is not widely 

 different from the proportion, always relative to the Pro- 

 jessional group as I.oo, in which the several occupations 

 are represented in the general male population, so far as 

 concerns the first six occupations. This means that in these 

 six occupations the total fertihty up to 1923, in the more 



