What’s the Difference? Understanding County- Versus City-Level Data

Dec. 19, 2018

Allegra Wilson and Samantha Breslin

Before the Dashboard’s launch in May 2018, there was a clear need for city-level data. Previously, most data on health and its drivers was not organized at the city level, but at national, state, or county levels. City leaders often used county-level data to evaluate city health and determine priorities, but this did not always capture the full story.

Austin Public Health was presenting to the City Council when a council member asked a question about data on his district, which straddles two counties: Williamson and Travis. They soon realized they needed access to data that was specific enough to address nuanced questions on community needs, considering the unique geography of the city. The Dashboard’s city- and neighborhood-level data helps fill this gap by helping city leaders better target their efforts to improve the well-being of residents, neighborhood by neighborhood.

But, the question remains, how exactly do city- and county-level data differ? Three geographic scenarios using the Dashboard’s children in poverty metric help illustrate the relationships between city- and county-level data.

  1. Cities that are a part of a single larger county area. This is the most common type of the city-county scenarios. Here, county-level data would include a population that is larger than the city’s population. Larger counties are likely to encompass suburban and/or rural areas, which often have health-related challenges and needs unique from urban areas. Larger counties can also fully include other cities.

    county vs city - wa

    In the image above, Washington state’s Pierce County (gray) covers and extends far beyond the Tacoma city boundaries (blue).

    Tacoma has a higher percentage of children in poverty (24.3%) compared to Pierce County (17.2%). As a result, the city-level data available on the Dashboard helps city officials paint a clearer picture of their community’s health, while county officials would want to look to the county-level data.

  2. Cities that are part of two or more counties. Seventy-six cities included in the Dashboard’s 500 cities are located in multiple counties. Cities that fall in multiple counties face the challenge of trying to combine multiple counties worth of data to understand their communities.

    county vs city - tx

    For example, the city of Austin, Texas (blue) spans three counties: Williamson, Travis, and Hays (gray). The levels of children in poverty are different in each of these four areas with Austin at 23.8 percent and Williamson, Travis, and Hays Counties at 8.9 percent, 21.2 percent, and 16.3 percent, respectively.

    The city of Austin has a higher percentage of children in poverty than the counties it spans. Because of this, using city-level data provides a better estimate of the percent of children in poverty in the city.

  3. Cities that align with one or more county. A few of the 500 cities, however, do match up with their county boundaries. For example, in Philadelphia, Pennsylvania, the city and county cover similar geographic areas and populations. In these cases, data for cities and counties are very similar or the same, as seen here with both the city of Philadelphia and Philadelphia County having the same children in poverty estimates (36.7%).

county vs city - pa

Through these three geographic scenarios, the public health field’s need for the City Health Dashboard is clear. “Before the Dashboard, we often relied on data which did not always reflect the stories or health challenges we were seeing,” shares Stephanie Hayden, the director of Austin Public Health. “The Dashboard gives us the ability to better address what is going on within the borders of our city and paint a clearer picture of the health of our constituents.”

Explore the Dashboard more to see all the ways you can use city-level—and neighborhood-level data—to better understand your city’s health and drive change in your community!

county vs city graphic

Learning More

Please visit County Health Rankings and Roadmaps if you are interested in county-level data.

1 Full list of the Dashboard’s aligning cities and counties:

Anchorage, AK (Anchorage Municipality); San Francisco, CA (San Francisco County); Denver, CO (Denver County); Washington (District of Columbia); Columbus, GA (Muscogee County); Lexington, KY (Fayette County); New Orleans, LA (Orleans Parish); Baltimore, MD (Baltimore County); St. Louis, MO (St. Louis County); New York, NY (Bronx County, Kings County, New York County, Queens County, Richmond County); Philadelphia, PA (Philadelphia County); Alexandria, VA (Alexandria City); Chesapeake, VA (Chesapeake City); Hampton, VA (Hampton City); Lynchburg, VA (Lynchburg City); Newport News, VA (Newport News City); Norfolk, VA (Norfolk City); Portsmouth, VA (Portsmouth City); Richmond, VA (Richmond City); Roanoke, VA (Roanoke City); Suffolk, VA (Suffolk City); Virginia Beach, VA (Virginia Beach City)

2 Estimates for children in poverty at the city-level are from the City Health Dashboard, using 2016 American Community Survey 5-year estimate data from the B17020 table.

3 Estimates for children in poverty at county-level are from 2016 American Community Survey 5-year estimate data from the B17020 table.

The 2017 city shapefile is from Centers for Disease Control and Prevention’s 500 Cities Project. It can be downloaded here.

The 2016 counties (and equivalents) shapefile is from the U.S. Census Bureau’s TIGER/Line® Shapefiles. It can be downloaded here.

Note: We use “aligned” in place of “coterminous” in this blog; however, readers should interpret the two to be equivalent in meaning.

Last updated: May 14, 2019

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