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Here there are 4 variants of a world population model.

1. Constant growth at 1.25% per year (this is only here as a fiducial)

2. Continuously exponentially declining population (probably unrealistic

3. Modified: Population continually declines until some threshold growth rate/fertility rate is reached and then it starts to rise again, continuously exponentially at the new constant rate which is the threshold.

4. Oscillatory: complicated but perhaps the most realistic; Like the modified, starts to rise again but then has a correction to mimic the decline. Also has a lag time parameter adjustment to account for response time to dwindling population. The effective growth rate for the oscillatory model is in Column L
   
   
   
   
   
   Week 6