
It is of interest to note that the increase during 1957 reverses 
a general decline in population which apparently began in 1953. 
Swan “ The 1957 swan index is 37 percent above the average 
for the. past eight years, and compared to individual-years is: 

8 percent below 1956 
21 percent above 1955 
57 percent above 1954 
52 percent above 1953 
114 percent above 1952 
34 percent above 1951 
148 percent above 1950 
12 
