The following is an audio transcript of the video lesson plan Power of the Pyramids.

Hello, my name is Katie and I will be demonstrating the lesson Power of the Pyramids. This lesson will help your students predict a nation’s population growth rate based on its current age and sex distribution.

We have two versions of this activity – one for Grades 6-8 and one for Grades 9-12. Today, I will be focusing on the high school version, which is more rigorous compared to our middle school version. This lesson could be used in a math, social studies, or science class and it is particularly well suited for unit 3 of AP Environmental Science and unit 2 of AP Human Geography.

By the end of the lesson, your students will be able to:

• Describe the three general shapes of population pyramids and their meanings.
• Construct a population pyramid for one of six different countries.
• Make correlations between the shape of a country’s pyramid and its growth pattern.
• Analyze countries’ population pyramids to make inferences about past events, current trends, and future growth.

Before we jump into the lesson logistics, let’s first review what population pyramids are and how to interpret them. A population pyramid, which is sometimes called an age-structure diagram, is a type of histogram that displays the proportion of age and sex in a given population.

Here is the population pyramid of the entire world. We can see here that on the y-axis we have five-year age cohorts. On the x-axis, we have the percentage of the total population, with the male cohorts on the left and the female cohorts on the right. Each cohort is a bar on the pyramid that represents the percentage of a population comprised of people of one sex within a certain age range. For example, if we look at the female cohort aged 0-4, we can see that demographic makes up just over 4% of the world’s population.

You’ll also see that our population pyramid is color-coded into three reproductive groups. This is only found in the high school version of the lesson. Pre-reproductive groups are children, who have not yet reached reproductive maturity. Then, our reproductive group represents people who potentially are biologically able to produce children. On the top, we have our post-reproductive group who are generally past their child-bearing years.

In the lesson plan, we provide data for six countries’ population pyramids. In the interest of time, you could have your students split into small groups to divide and conquer the graphing.

In this video, I will be constructing just the population pyramid of one country – Nigeria. If you’d like your students to practice some computational skills, we do have a worksheet with the population data that has students calculating the percentages for each age-sex cohort. If you are short on time or want to focus on other skills for this lesson, you can always provide the population data with percentages already filled in, which is what I will be using in this video.

Now, let’s make our pyramid!

Let’s look at our population pyramid for Nigeria and see what information we can glean from this data. What I immediately notice is that it is triangular in shape; it’s bottom-heavy. This tells us that the population of Nigeria is disproportionately composed of young people. We can tell because the younger the cohort, the wider the bar is that represents their demographic. So a plurality of Nigeria’s population has not yet reached reproductive maturity. So, there is a lot of potential for future population growth once Nigeria’s pre-reproductive cohort reaches their child-bearing years.

Let’s take a look at all 6 of the countries your students will graph in this lesson.

Based on Nigeria’s pyramid shape, we were able to infer that it is growing. Which of these populations do you think is growing at the slowest rate? The answer is Germany, which is actually experiencing negative population growth. We can tell because of its pyramid shape. In fact, it has kind of an inverted triangle shape. The largest age demographic is people in their 50s. And the smallest age demographic is people who are not yet biologically able to have children. So by the time they can have children, there is a smaller reproductive cohort than there was in years past.

When we look at the United States pyramid, we can see that it is almost rectangular in shape. This tells us that each age cohort is more or less uniform. That means that the population of the United States is mostly stable.

Quick side note: we do have both the middle and high school versions of this activity that use Canada’s population pyramid in place of the United States. The shapes of these two pyramids are very similar.

But back to the pyramids on the screen. Guatemala and India are also interesting to observe here because, just like Nigeria they have that triangular shape. However, the base of Nigeria’s pyramid is wider than that of Guatemala or India. We can also tell that of these three countries, India has the slowest population growth rate because its base is narrowest. In fact, the base of India’s population pyramid is rectangular, which shows that their population growth rate is slowing. In 1970, India’s total fertility rate was about 5.6 and today it is a little over 2.

So as you analyze these pyramids with your students there are a variety of provided questions you can have them discuss. For example, you can have them hypothesize various historical moments that are represented in the population pyramids. See if they can identify the impact of the baby boom in the United States or the one-child policy in China.

And that’s the lesson Power of the Pyramids. For more fantastic lesson plans and classroom resources related to populations, visit our website at populationeducation.org!