MODEEN PEOBLEMS 321 



slow in countries which already use these methods, and thus, so 

 long as the knowledge of the arts of production is not equal in all 

 countries, different rates of increase are liable to arise when 

 knowledge spreads into a more backward country .^ 



Such changes are altering the composition of the population 

 of the world. The following figures have been given for Europe. 

 Out of 1,000 inhabitants there were in the years named the 

 following proportion of Teutonic, Eomance, and Slav elements : 



> Leroy-Beaidieu estimates that, if the degree of skill in production now found 

 in Western Europe was extended throughout the world, the population economically 

 desirable would be from two to three times that of the present population of the 

 world {Question de la Population, p. 174). 



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