HUMAN LONGEVITY 



79 



the reverse situation obtains as in the populations of France 

 and Sweden, the number of workers still remains constant at 

 about 50 per cent, and so does the total load they have to carry. 

 As we go down the table it is seen that as the first column of 

 figures — the percentage in the population of persons in the pre- 

 reproductive period — decreases, the figures in the last column 

 increase — the percentages in the post-reproductive period. 



THE LIVmG POPUJi^TIOn 



The 



Old 



50&'0vet 



Fig. 15, Approximate averag-e distribution of living- human population. 



Frequencies are depicted as areas. 



The situation may be graphically generalized in the manner 

 shown in Figure 15. 



The bottom half of the square, representing half the popula- 

 tion, supports the upper half, which may be divided variously 

 between the children and the old, but always still remains 

 about a half of the total population. 



On the basis of this natural biological classification of the age 

 distribution Sundbarg distinguishes three types of fopulatiofiy 

 the progressive type, the stationary type, and the regressive 

 type. His definitions of these types are that, on a percentage 



