1. Do Now: ► How fast is the worlds population growing? Which country is growing at the fastest rate?

2. Aim: How can we calculate human population growth?

3. Fig. 11.3, p. 240 <1% 1-1.9% 2-2.9% 3+% Data not available Annual world population growth Population Growth Rate

4. By The Numbers… ► What variables do we take into consideration when determining the size of a countries population?

5. An example… ► Let’s say a country has a population of 30,000,000.  Births = 390,000immigrants = 220,000  Deaths = 210,000emigrants = 60,000 ► How can we figure out how fast their population is growing?

6. ► Birth Rate – the number of people born per year x 1000 population population For example: BR = 390,000 x 1000 30,000,000 30,000,000 BR = 13 (this country had 13 people born per 1,000 people in that country)

7. ► Death Rate – the number of deaths per year x 1000 population population For example: BR = 210,000 x 1000 30,000,000 30,000,000 DR = 7 (this country had 7 people die per 1,000 people in that country)

8. ► Growth rate = birth rate – death rate Example: 13 – 7 = 6 (per 1000) This means that the natural increase rate for this country is 6 people per 1000

9. ► The Rule of 70 (Doubling Time) ► ► Rule-of-70 - way to calculate the approximate number of years it takes for the level of a population growing at a constant rate to double.  States that the approximate number of years n for a variable growing at the constant growth rate of r percent, to double is: n = 70/r

10. ► The Rule of 70 (Doubling Time) 70 70 Population Growth Rate (as a percent) Population Growth Rate (as a percent) 70 = 63.6 years 70 = 63.6 years 1.1 1.1 What this tells us is that the population of that country will double in 63.6 years.

11. ► Example – The African country of Togo Togo has a population growth rate of 3.6% 70 = 19.4 years 70 = 19.4 years 3.6 3.6 The population of Togo will double in under 20 years!

12. Time to practice…. ► Population Math Lab

13. The end….