Planting new forests make no difference as the location of rubber is pre detemined when the game starts. Which does also mean that if you cut a forest down ealier in the game which would of had rubber in it it will still be there just on a different tile to what you would normally expect.
I thought something like half the population was converted to workers when you raze? I haven't done much razing recently though, and don't know for sure...
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