220 



THE SOCIAL LIFE OF ANIMALS 



ure 43) shows that beginning in 1934 there has been 

 a dramatic decrease in the percentage of births can- 

 celed by deaths; actually there has been a decided 

 increase in births. Recent analyses in the American 



1928 1929 1930 1931 1932 1933. 1934 1935 



Fig. 43. The percentage of births that were canceled 

 by deaths for the given years in Italy and Germany. The 

 higher the trend line, the slower the population is grow- 

 ing and vice versa. The broken line connects the ob- 

 served points; the solid line shows the mathematically 

 smoothed trend line. (Data from The Statesman's Year 

 Book.) 



