World in the Balance
 
Student Handout

Calculating Population Growth
Use the instructions on this handout to calculate population growth estimates
for your assigned countries.
Procedure
Multiply the initial population by the growth rate. This will give you the
number of individuals that are added to the population in a 10year period.
(This number should be rounded up, since partial individuals do not exist in
the real world.)
Add the result from Step 1 to the initial population to get the new
population after 10 years.
For the next 10year period, the new population size becomes the starting
population value. Multiply the new population size by the growth rate. As
before, add the resulting number of individuals to the starting population to
calculate the new population size after 20 years.
Repeat the process until each country's population has doubled. Note that
because you are looking a 10year periods, the population may not be exactly
double in size at the end of a period. For instance, in the example given, you
would stop after 30 years, when the population reaches 124.
Sample Calculation
Here is a sample calculation for a country with a 10year growth rate of .25.
The country's population doubles soon after 20 years.

Starting
Population

10year
Growth Rate

Number
of New Individuals

New
Population Size
 
Initial 
50 
.25 
12.5
(13)

63  
After
10 years

63 
.25 
15.75
(16)

79  
After
20 years

79 
.25 
19.75
(20)

99  
After
30 years

99 
.25 
24.75
(25)

124  
