Breeding-population Index (millions) 
Figure 2. 
Trends in Breeding-population Indexes 
by Management Units, 1953-1960 
70 
60 7 
CENTRAL a 
Pin wf : 
“ ~ee, it 
Pa 
40 f 
30 
WESTERN 
an TES, pee eT 
ee een ee ee 
Panel 
aw ‘ 
10 

1953 1954 
EASTERN 

1955 1956 1957 1958 1959 1960 
