note of 10/31/2018

population pyramids
we use population pyramids to analyze growth ( or decline) of fertility mortality, and migration in cities
male is always on the left side and female is always on the right side
the kiddos under20
economically active 20-64
the oldies above 65
there are three basic types
the xmax tree:developing nation, growth rate is slow, high birth rate, short life expectance
the box:developed country, slow growth ,low infant mortality, slow population growth, long life expectancy
the cup: developed country, negative growth, low birth rate shrinking population, long life expectancy