locate and extract census data;
produce population density maps of the United States in different scales;
analyze population density maps by observing patterns and drawing conclusions;
determine how different scales of analysis can produce different patterns of population density and influence interpretations of that data; and
understand population density maps as a tool for marketing products.
Asking Geographic Questions
Acquiring Geographic Information
Organizing Geographic Information
Analyzing Geographic Information
S u g g e s t e d P r o c e d u r e
Instruct students that they work for a retail company (keep vague; see "Suggested Student Assessment" below) that plans to open a few stores but only in the states with the greatest concentration of people.
Encourage students to suggest ideas for accurately locating the greatest concentrations of people.
Help students develop a definition of population density. Have them research the land area in square miles (or square kilometers) and resident population for each state, then calculate the population density. Be sure they are using data from the latest census. The U.S. Census Bureau's Population Estimates Program is the best source for this kind of information. [Note: Data from the 1990 census is provided in the population data table below if you choose not to have students gather the data.]
Use the formula Population density = Population/Land Area to calculate the density for each state and the entire United States. Do not include the District of Columbia in your calculations. Be sure to record your correct answers in the table. Hint: To calculate the average for the entire United States, first add the populations of all 50 states. Then add the land area of all states. Divide the total population by the total land area. [Note: Students can check their work at the U.S. Census Bureau's table, Land Area, Population, and Density for States and Countries.]
On their outline maps of the United States, have students use different colors or patterns to indicate those states that have a population density greater than the United States average (70 people per square mile) and those states with a population density less than the United States average. The rule of thumb is the higher the value, the darker the color. Use your lightest color for the "less than" category and your darkest color for the "greater than" category.
Observe the spatial distribution. Ask students what patterns can be seen in the distribution of population densities by state. What inferences can you make by observing the overall spatial distribution?
Create a map with a different, more detailed scale of analysis. Provide students with another blank outline map of the U.S. Instruct them to label with different shades states with population densities that fall into the following ranges:
less than 70 people (U.S. average) per square mile (2.6 square kilometers)
between 70 and 140
between 140 and 280
between 280 and 560
560 or more
Analyze the map. Ask students what patterns they observe on their new maps. Do they note clusters of population, or is it evenly dispersed? What factors could account for the patterns they see? What would happen to the average population density if we counted the District of Columbia, a city, as a state instead?
Compare the maps. Thinking like a geographer requires looking at issues from a variety of perspectives and at a variety of scales. Ask small student groups to answer the following questions:
How does the added detail in the five-category map affect population density observation and interpretation?
What conclusions can you draw from the five-category map that you cannot from the two-category map?
What general statements can you make about the spatial distributions shown on maps? (Students, it is hoped, will recognize that maps created from spatial data can be manipulated to create different spatial distributions. This in turn will influence inferences drawn from the maps.)
Which map would the students use to determine the states in which to open the new stores? Why?
Suggested Student Assessment:
To assess whether students can gather appropriate data and create a five-category population density map as taught in this lesson, split the class into groups and assign them different kinds of retail companies (e.g., youth interest, senior interest, men's clothing, women's clothing). For their map, have students show the density of the particular market set for their assigned company. After creating a map, students should be able to write an essay or give a verbal report that convincingly suggests in which states their company should locate its next five stores. The report or essay should describe the kind of map needed for their decisions and their reasons for using that map.
Extending the Lesson:
Encourage students to use this same technique (applying geographic data to a map) as part of a report for a different class. Data is available for other countries and regions. Explore patterns in age distribution, for example, by finding the percentage of people under age 18 for several countries within a region or a continent. What significance does a very young population have for a country? A very old population?