A--overpopulation
B--under population
C--working population
D--population waiting for employment
E-- population
F--rural population
G--population reproduction
H--population increase
I--population decrease
J--population base
K--population distribution
L--population density
M--population quality
N--population pyramid
O--population statistics
P--population theory
Q--population studies ( ) 在业人口 ( ) 人口密度