Do Now: Do Now: ►How fast is the worlds population How fast is the worlds population

growing? Which country is growing at growing? Which country is growing at the fastest rate? the fastest rate?

Aim: How can we Aim: How can we calculate human calculate human

population growth? population growth?

Fig. 11.3, p. 240

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Annual worldpopulation growth

Population Growth Rate

By The Numbers…By The Numbers…►What variables do we take into What variables do we take into

consideration when determining the size of consideration when determining the size of a countries population?a countries population?

An example…An example…

►Let’s say a country has a population of Let’s say a country has a population of 30,000,000.30,000,000. Births = 390,000Births = 390,000 immigrants = 220,000immigrants = 220,000 Deaths = 210,000Deaths = 210,000 emigrants = emigrants =

60,00060,000

►How can we figure out how fast their How can we figure out how fast their population is growing?population is growing?

►Birth RateBirth Rate – – the number of people born per yearthe number of people born per year x 1000 x 1000 populationpopulation

For example:For example:

BR = BR = 390,000 390,000 x 1000 x 1000 30,000,00030,000,000

BR = 13 (this country had 13 people born per BR = 13 (this country had 13 people born per 1,000 people in that country) 1,000 people in that country)

►Death RateDeath Rate – – the number of deaths per yearthe number of deaths per year x 1000 x 1000 populationpopulation

For example:For example:

BR = BR = 210,000 210,000 x 1000 x 1000 30,000,00030,000,000

DR = 7 (this country had 7 people die per DR = 7 (this country had 7 people die per 1,000 people in that country) 1,000 people in that country)

►Growth rate Growth rate = = birth rate – death ratebirth rate – death rate

Example:Example:

13 – 7 = 6 13 – 7 = 6 (per 1000)(per 1000)

This means that the natural increase rate This means that the natural increase rate for this country is 6 people per 1000for this country is 6 people per 1000

►The Rule of 70 (Doubling Time)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 States that the approximate number of years n n for a for a variable growing at the constant growth rate of variable growing at the constant growth rate of r r percent, to double is:percent, to double is:

n = 70/rn = 70/r

►The Rule of 70 (Doubling Time)The Rule of 70 (Doubling Time)

70 70 Population Growth Rate (as a percent)Population Growth Rate (as a percent)

70 70 = 63.6 years = 63.6 years 1.11.1

What this tells us is that the population of that What this tells us is that the population of that country will double in country will double in 63.6 years63.6 years..

►Example – The African country of TogoExample – The African country of Togo

Togo has a population growth rate of 3.6%Togo has a population growth rate of 3.6%

70 70 = 19.4 years = 19.4 years 3.63.6

The population of Togo will double in under 20 years!The population of Togo will double in under 20 years!

Time to practice….Time to practice….

►Population Math Lab Population Math Lab

The end….The end….