U.S. Population Growth: What Does the Future Hold?
College Algebra or Liberal Arts math students are presented with a ConcepTest, a Question of the Day and a write-pair-share activity involving U.S. population growth. The results are quite revealing and show that while students may have learned how to perform the necessary calculations, their conceptual understanding concerning exponential growth may remain faulty. Student knowledge (or lack thereof) of the size of our population and its annual growth rate may also be surprising.
- gain some knowledge of the size of our U.S. population and its projected growth
- develop a deeper understanding of exponential growth
- recognize the differences and similarities between linear growth and exponential growth
- recognize the effect and implications of long-term exponential growth even when the growth rate is relatively small
Context for Use
The time required for the entire activity is approximately 25-30 minutes but fewer segments can be offered as a shorter alternative (see Activity Description below for individual segment times).
Description and Teaching Materials
- Students are given a ConcepTest (Rich Text File 26kB Jul9 07) in the form of a straw poll (either show-of-hands or written) concerning the current U.S. population, its current growth rate, and a projection concerning the population in 2050. Each student is asked to make a conjecture and the instructor records the results for the class to see. (~5 minutes)
- The Question of the Day (Rich Text File 17kB Jul9 07) addresses the difference between a ten-year growth rate and an annual growth rate and also addresses the similarities and differences between linear and exponential growth. It begins with three ConcepTest questions and then students work in pairs to share and explain their answers and reasonings in written form. The instructor will need Internet access and a projector to display the specified population graphs for student viewing. (~10 minutes)
An easy-to-use tool for investigating U.S. demographic trends created and developed by the Social Science Data Analysis Network (SSDAN) at the University of Michigan.
- MERLOT description of CensusScope
- U.S. Census Charts and Tables
U.S. Census Bureau data made more accessible and readable.
- MERLOT description of this Census Bureau data
- Lastly, students are asked to construct an exponential growth model and calculate future population values with the help of a graphing calculator in a write-pair-share activity (Rich Text File 86kB Jul9 07). They are also asked to describe and record the implications of these projected values. (~5-10 minutes)
- In conclusion, the instructor presents a summary of student results (~5 minutes)
Teaching Notes and Tips
Lastly, the write-pair-share activity is designed to bring them to a realization of the dramatic results of our population growth if it were to continue at its present growth rate. Most students have never considered the mathematics involved and are somewhat shocked at the results.
References and Resources
Provides on-line access to census data, publications, and products
MERLOT description of the U.S. Census Bureau site
Direct link to the U.S. Census Bureau site