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

Aim: How can we calculate human population growth?

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

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

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?

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

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

► 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

► 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

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

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

Time to practice…. ► Population Math Lab

The end….