A new interactive tool shows the change in population between 2010 and 2020 for each of the country’s 85,000 census tracts. The new higher resolution map adds detail to a decade of population change across the US.

When detailed 2020 Census data was released in August 2021, the disparity of population change among the nation’s more than 3,000 counties was clear. Less than half of U.S. counties saw increases over the last decade. Most gains were concentrated in larger cities and their nearby suburbs, while most rural counties generally trended downward.

A new visualization tool from the Tennessee State Data Center at the University of Tennessee, Knoxville, adds a higher level of resolution to the population changes occurring between 2010 and 2020 across the country.

Small statistical areas called census tracts were the basis for a calculation of the 10-year population change. The new subcounty data highlight some interesting patterns that were not as discernable on county-level maps.

Most notable is the strength of the population increases at the outer-suburban fringe of many metropolitan areas. In these locations, the existing suburban development pattern is extended on ample and more affordable land found further from the urban core.

Figure 1:  Census tract-level change in Charlotte and Houston Metros. Areas in darker shades of green ringing the core-city saw a larger population increase between 2010 and 2020 than census tracts that were lighter shades of green. Areas in grey lost population.

Population increases closer to the urban core, where most land is already developed, were weaker by comparison. Growth was already slowing in the country’s large cities over the past decade, but the onset of the COVID-19 pandemic might have accelerated it.

This pattern of change at the suburban fringe was evident in many of the largest metros like Houston and Atlanta, but the trend in smaller metropolitan areas was similar. Kansas City, Indianapolis, Columbus and Greenville (SC) were just a few of the communities that saw their fastest growing areas located on the flanks.

“We don’t want to give the impression that population increases in suburban areas are a new occurrence,” said Tim Kuhn, Director of the Tennessee State Data Center. “This kind of suburban expansion has happened for decades. What’s unique is the ability to visualize this type of change across such a large area of the country so that we can make these comparisons.”

It’s also easier to see the areas that experienced population loss last decade. Along the length of the Mississippi River valley, the new map adds detail to a region that experienced protracted population declines – with some county populations having peaked in the 1970s and ’80s.

Several major cities along this corridor recorded population declines last decade, including Saint Louis and Memphis. The map helps to identify neighborhoods within these communities where population fell.

Figure 2:  Census tract-level change in the Saint Louis and Memphis Metros. Both communities had declining population in the principal city of the Metropolitan Statistical Area. Along the length of the Mississippi River valley many rural areas also saw continued population declines.

“This is a useful tool for visualizing how communities have changed over the last 10-years, but we can extend this work to better characterize locations where population is stabile, increasing and decreasing,” Kuhn said.

This could include creating aggregate measures of change across communities that help show how cities in different regions of the country or of varying size changed over the decade.

In support of those efforts, the State Data Center published its census tract-level map data to enable further analysis by other agencies, intuitions and data users.

The project incorporated decennial census data from the U.S. Census Bureau and IPUMS National Historic Geographic Information System (NHGIS). Users can also leverage data from Brown University’s Longitudinal Tract Database to perform similar types of analysis that includes additional historic data and variables.

Read more about how the data was created on our website.