The County Health Rankings, a program of the University of Wisconsin Population Health Institute, measures the health of nearly all counties in the nation and ranks them within states. The Rankings are compiled using county-level measures from a variety of national and state data sources. These measures are standardized and combined using scientifically-informed weights. To learn more about research on our methods, see our selected publications.
We suggest starting with the County Health Rankings model. It provides the foundation for the entire ranking process. Counties in each of the 50 states are ranked according to summaries of a variety of health measures. Those ranking in the healthiest 75-100% of counties are considered to be the “healthiest.” Counties are ranked relative to the health of other counties in the same state.
How CHR&R measures are selected
The County Health Rankings team goes through a careful and deliberate process when selecting measures for inclusion. We consider measures that meet our program's goals, ensuring they reflect important aspects of population health that can be improved, and we consider measures that are innovating to meet the needs of communities. Our measures are also selected based on their technical and analytical feasibility, ensuring they are not limited by availability, cost, validity, coverage, or other concerns.
The County Health Rankings team draws upon the most reliable and valid measures available to compile the Rankings. Where possible, we provide the margins of error (95% confidence intervals) for our measure values. In many cases, the values of specific measures in different counties are not statistically different from one another; however, when combined using our model, those various measures produce different rankings.
What's a county?
The County Health Rankings are based on counties and county equivalents (ranked places). Any entity that has its own Federal Information Processing Standard (FIPS) county code is included in the Rankings. We only rank counties and county equivalents within a state. The major goal of the Rankings is to raise awareness about the many factors that influence health and that health varies from place to place, not to produce a list of the healthiest 10 or 20 counties in the nation and only focus on that.
Calculating quartiles and county ranks
The County Health Rankings are compiled from many different types of data. To calculate the ranks, we first standardize each of the measures using a z-score. The ranks are then calculated based on weighted sums of the standardized measures within each state. The county with the lowest z-score (best health) gets a rank of #1 for that state and the county with the highest score (worst health) is assigned a rank corresponding to the number of places we rank in that state. Counties are then grouped into four equally sized groups (quartiles) from Least Healthy to Healthiest (Lowest 0-25%, Lower 25-50%, Higher 50-75%, and Healthiest 75-100%) within each state. The county with a rank of #1 can be found in the Healthiest (Healthiest 75-100%) quartile.