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Grade 9-12

Population Growth: Friend or Foe?

Updated: March 28 2014,
Author: Melanie Marks


The environment has recently been the focus of much research and discussion.  Because productive resources are limited, it is important that we use resources wisely to ensure that resources will be available for use in future generations.  Of concern to both environmentalists and economists are the trends in the U.S. & World Population Clocks .

See this related article: "World Population: A Major Issue for the Millennium"

crowdOf primary importance is the population growth rate.  The population growth rate measures the percentage increase in a population.*  For example, if the population growth rate for a given country is 1.2, then population in that country has increased by 1.2%.  Of course, the population growth rate could be negative.  A growth rate of -.01, for example, would mean that the population has decreased by .01%.

If the population growth rate is rising over time, then the size of the population is growing at an increasing rate.  For example, in 1960 the world population was at 3,039,451,000.  In 1961 56,010,616 people were added to the planet (a 1.8% increase); in 1962 69,397,019 were added to the planet (a 2.19% increase.)  The rising rate means not only that population is increasing, but that it is increasing at a faster and faster pace.

Task List

In this lesson you will calculate population growth rates, use Bureau of Census data to find statistics on specific countries, compare the population situation in More Developed Countries (MDCs) to that of Lesser Developed Countries (LDCs), calculate how long it will take a country's population to double, and discuss the idea of using government policy to control population.


Identifying the Trends

In order to learn about the trends in world population for the years 1950-1998, you can access data made available on the Bureau of the Census Page on World Population .  Use the data to answer the following questions.

Question 1   

  1. Discuss some of the general trends you observe for the years between 1950 and 1998.
  2. What trends are forecast for 1999-2050?

Question 2

  1. What resources are important for sustaining life?
  2. How might an increasing population affect the supply of these resources?
  3. How is your answer in (b) related to the concept of scarcity?
  4. How does our government help to save resources?

Calculating Population Growth Rates

babyPopulation growth rates are simple to calculate.  You need only two numbers in order to determine how fast a population grows.  The first is a country's Birth Rate.  Birth rate is the number of births per 1,000 people for a given year.  For example, if a country had a birth rate of 20 in 1998, that means there were 20 babies born per 1,000 people.  (Thus, if the country has 100,000 people, it can be estimated that the number of births was 2,000).  The second number needed is the Death Rate.  The death rate tells the number of deaths per 1,000 people for a given year.  If a country had a death rate of 15 in 1998, this means that an estimated 15 people died for each 1,000 citizens in that year.  (See an example of birth and death rates for Afghanistan in the Afghanistan Factbook .)

Calculating population growth rates is straight-forward.  You simply plug birth rates and death rates into the following equation: 

 % Growth Rate = (BR-DR) / 10.

For example, Brazil had a birth rate of 21 and a death rate of 9 for 1998.  Plugging this into the above equation gives = (21 – 9) / 10 = 1.1%, which tells us that the population of Brazil grew by 1.1% in 1998.

Question 3

Is there anything related to population that is not captured in the growth rate equation?  Can you think of something that helps determine a country's population but is not a birth or a death?

Comparing MDCs and LDCs

There are clear patterns of population associated with More Developed Countries (MDCs) versus Less Developed Countries (LDCs).  MDCs are countries that have relatively high per capita incomes (income per person) and standards of living.  These countries have experienced long-term economic growth and they are technologically advanced.  Some examples of MDCs are the United States, Germany, and England.  LDCs are countries that have not benefited from long-term economic growth.  LDCs have relatively low standards of living and low per capita incomes, and they generally rely on developed countries for technology.  Countries such as Tanzania and Ethiopia are considered LDCs.

Start by completing the following tables.  Use the Bureau of the Census page that details Country-Specific Population Information .  You will have to go to the chart with the country names and highlight the specific country for which you would like data.  Then click on "Submit Query."  You will connect with a data set.  Notice that the first two lines of the data provide the country's birth rate and death rate for the year for which the most recent data are available (currently, 1998).  You will have to do this for each country on the chart.

Fill in the blank spaces in the table, using the equation for calculating population growth rates and the country-specific data.

Table 1. Population Growth Rates for MDCs                                                                                      


Pop. Growth Rate















United Kingdom


United States




Table 2. Population Growth Rates for LDCs


Pop. Growth Rate



















Question 4

  1. Which country has the highest population growth rate?
  2. Which country has the lowest population growth rate?
  3. Does any country have a population growth rate that is less than 0?  If so, what does this mean?
  4. Can you form a general conclusion about how population growth rates differ for MDCs versus LDCs?

How is the United States Doing?

Answer the following questions so that you can make a conclusion about population growth in the United States.

Question 5

  1. In respect to population growth, how does the U.S. compare to other MDCs?
  2. How does the U.S. compare to the LDCs?
  3. If you were asked whether or not the United States has a population problem, what would you answer? Why?

How Long Will It Take a Population to Double?

beachThere is a very simple way to estimate how many years it will take for a country's population to double (this is called the "doubling time").  Use the following equation to calculate this information.  Simply take the number 70 and divide by the country's population growth rate:
  # of years for the population to double = 70 / (growth rate)

[NOTE: This calculation yields only an estimate. This method of calculating the doubling time assumes that the growth rate will stay constant.  Clearly, population growth rates change over time.]

Question 6

  1. Using the growth rates you calculated in Task 3, calculate the doubling times for the United States, France, Zimbabwe, and Ethiopia.
  2. What conclusions can you make about doubling times in MDCs versus LDCs?

Controlling Population Growth–The Case of China

Americans are free to have as many children as they wish.  In China, the government restricts the number of children each family can have.  Children must be "registered," and families that exceed the allowable number of children will not be given important resources–for example, education for the extra child.  The goal of the Chinese government is to reduce the rate of population growth in China.  However, there are other social implications of this policy.   Read the article "6.3 Brides for Seven Brothers " to learn more about the situation in China. 


  1. In China, what is happening to the population of boys as compared to the population of girls?
  2. What long-run problems has the one-child policy created?
  3. How do you think Americans would react if the U.S. government imposed this type of regulation?


Environmentalists and economists have studied trends in population growth. As population grows, resources will be used up faster and faster and more pollution will be created. The rate of population growth is an important variable and for years, population was growing at an increasing rate. Fortunately, population growth rates are now decreasing, which means that population is still growing but at a slower rate than before. While this unit does not address all aspects of the population debate, it does provide an introduction to the topic.