Why do people migrate ?

Push forces
- civil war
- environmental degradation 
- unemployment or underemployment 
- religious or ethnic persecution 


Pull forces
- better economic opportunity 
- better health services
- religious freedom 
- political freedom 

Total fertility Rate 

TFR- average number of children born per women 

for a population to remain the same, the TFR is 2.1 

higher then 2.1 population rises 
lower then 2.1 population falls 

world TFR 2.47
was 2.54 2 years ago 

US TFR - 2.06
Nigeria TFR - 5.38
Japan TFR - 1.39