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Thinking Complexity

21 Jan 2018, 02:45 PM
Chapters 3 › Unit 3: Charting stocks View instructions Hide instructions

Charting stocks

This exercise will help you practice your bathtub thinking skills. It has two parts.

  1. The population at the end of 2015 on Caiman Island was 10,000 people. The number of births is 100 people per year. The number of deaths is 60 people per year. What will the population be at the end of 2016? Assuming that flows are continuous, chart the flows and the stock over 1 year (2016).
  2. What will the population be at the end of 2019 (in 4 years) if births increase to 160 people/year for years 3 and 4? Assuming that flows are continuous, chart the flows and the stock over this four year period.

Hint: Don't forget that (1) a stock accumulates the net flow and (2) the slope of the stock curve is equal to the rate of the flow at the same point in time.

A suggested worked solution is provided in the references.

Population changes 2016 to 2019

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2016: Population + (Inflow - Outflow) = 1000 + (100-60) = 1040
2017: 1040 + (100-60) = 1080
2018: 1080 + (160 - 60) = 1180
2019: 1180 + (160 -60) = 1280

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