Analyzing the Mean Center of Population Movement for Individual States, 1900 to 2010

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06-03-2011 07:06 AM
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In my last blog, I discussed a new lesson and data set, entitled “Population Drift: Mean Center Analysis 1790-2010” in the ArcLessons library, which uses spatial analysis, spatial statistics, and GIS to determine and analyze the population centers of the USA and individual states over space and time, from 1790 to 2010. One of the most fascinating parts of this lesson is examining the movement of state population centers.


This map shows the movement of mean center for each of the 48 states from 1900 to 2010, with the 1900 center shown as a blue square and the 2010 center shown as a red square. Nevada’s mean center of population moved the farthest, making a beeline north to south from the mining areas near Virginia City in 1900 toward fast-growing Las Vegas. Similarly, the influx of residents to southern California and the decline of mining tugged California’s mean center toward Los Angeles, though the San Francisco Bay cities kept the center from moving as much as in Nevada. Colorado’s mean center moved from the Rocky Mountains to the Great Plains, inexorably toward Denver. In Kansas, the center moved west until 1920 as the high western plains were settled, but then reversed as a result of high plains population loss beginning with the Dust Bowl and continuing to the present day. Why did Virginia’s center move north? Why did some state centers move very little? In which state is the population center the furthest from its geographic center?

How might you use this lesson and data set to teach about the many economic, political, demographic, and perceptual forces that pull on the population center of each state? Where will these centers move in the future? How might you use these same techniques to analyze how the population center of a metropolitan area or a county moved over time? How might you use GIS to determine where the mean center of ethnic groups in your community or people of specific age ranges are located? Why are these centers not necessarily in the same location as the mean center for the whole population?

- Joseph Kerski, Education Manager
About the Author
I believe that spatial thinking can transform education and society through the application of Geographic Information Systems for instruction, research, administration, and policy. I hold 3 degrees in Geography, have served at NOAA, the US Census Bureau, and USGS as a cartographer and geographer, and teach a variety of F2F (Face to Face) (including T3G) and online courses. I have authored a variety of books and textbooks about the environment, STEM, GIS, and education. These include "Interpreting Our World", "Essentials of the Environment", "Tribal GIS", "The GIS Guide to Public Domain Data", "International Perspectives on Teaching and Learning with GIS In Secondary Education", "Spatial Mathematics" and others. I write for 2 blogs, 2 monthly podcasts, and a variety of journals, and have created over 5,000 videos on the Our Earth YouTube channel. Yet, as time passes, the more I realize my own limitations and that this is a lifelong learning endeavor and thus I actively seek mentors and collaborators.