lotka: a natural population norm 



247 



The value of the constants A, A' can be determined in a given 

 numerical example by graphic integration. Using the data given 

 in the Supplement to the Forty-Fifth Annual Report of the 

 Registrar-General of Births, etc., in England, covering the decen- 



Fig. 4. Relation between birthrate per head b, deathrate per head d and natural 

 rate of increase r in a population with stable age-distribution (on the basis of statis- 

 tics for England and Wales 1871-1880). 



nium 1871-1880, the numerical values shown in Table I were 

 obtained, partly by the aid of the planimeter and partly by appli- 

 cation of Simpson's Rule. 



Using the values of the constants thus obtained, and substitu- 

 ting for r the observed values, as given in the source cited above, 



