Watt Watchers of Texas: Texas is Too Good To Waste™

Activity: Modeling Population Growth

Grade Level:

Activity Overview: The key underlying demographic trends that strain energy and water resources are population growth and economic growth. Other key trends are the impacts of global climate change and policy choices, whereby policy makers push for more water-intensive energy and more energy-intensive water.

As the population increases, more people demand more energy and water. However, because of economic growth, which happens in parallel, the demand for energy and water increases faster than the population.1 This phenomenon occurs because economically affluent populations tend to consume more energy and water per person than poorer populations.

Problem Statement:

Describe the nature of exponential growth in human populations.

Project Deliverables:

Students should use technology to research global historical estimates and population records. They should then create a mathematical model based on the data. Many population curves exist online, but students should not copy and paste them for the purpose of this assignment.

After creating their models, students should compare them with the widely accepted population curves to see how well they have modeled historical population trends. Historical data will not allow for the creation of predictions of the future, but many of the population curves will contain future predictions based on possible trajectories for population growth.


Exponential population growth can be represented using a simple J curve, but reality is more complex and limited, and could be represented using an S curve.

The United Nations Population Division produces official United Nations population estimates and projections.

The United States Census Bureau has collated many different resources into a comprehensive historical estimate of world population.

The attached table is composed of the summary values of Historical Estimates of World Population from the United States Census Bureau. The spreadsheet program automatically generated the scatterplot, which was then adapted to a logarithmic scale in order to better show the trend. Since 1900, there is a slight downturn in the rate of population growth. The exponential trendline superimposed over the scatterplot resembles the sigmoidal curve above.



  1. Jill Boberg, Liquid Assets: How Demographic Changes and Water Management Policies Affect Freshwater Resources (Santa Monica: RAND Corporation, 2005); Peter H. Gleick, ed., Water in Crisis: A Guide to the World’s Fresh Water Resources (New York: Oxford, 1993); reports and data from the U.S. Energy Information Administration; and reports from the International Energy Agency.
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