1. Population Growth Calculations: Exponential Growth, Rule of 70 & Doubling Time
Ch. 6

2. How Has Human Population Changed Over Time?*

3. Human Population is Growing Exponentially*

4. Exponential Growth
When a quantity increases at a fixed percentage per unit of time.
Example: 2% per year

5. Exponential Growth Example
$100 invested at 7% a year annual compound interest will double in 10 years

6. Exponential Growth Example
Applies to populations too! If a population grows at 7%/year it will double in 10 years!
100 people, 10 years = 200, 20 years = 400, 40 years = 800. With doubling time and population growth, things get bad in a hurry.

7. Doubling Time
The time it would take for population to double if it were growing exponentially at a constant rate.

8. Rule of 70
A trick to estimate population doubling Doubling Time (years) 70 =
% Growth Rate

9. Population Density

10. Birth or Death Rate

11. Population Growth Rate (r)