cr: Crowding Ratio
Variable
Global
Crowding Ratio []
cr = p /( la * pdn )

cr in the updating graph: ( how to read )
In nodes
la : land area (square kilometers)
p : population
pdn : population density normal (people/square kilometer)
Out nodes
brcm : birth-rate-from_crowding multiplier
drcm : death-rate-from-crowding multiplier
fcm : food-from-crowding multiplier
qlc : quality of life from crowding