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. The FIPS county code is a five-digit code where the first 2 digits represent the state and the remaining 3 digits designate county or county equivalent. Certain major cities, such as Baltimore and St. Louis, are considered county equivalents and have their own FIPS county code. Other cities, such as Chicago, do not have a FIPS code and are not individually ranked.
During the last decade, several county definitions have changed due to merging with another county, being dissolved and distributed into other counties, or undergoing a name change. Please read our FAQ to find more information.
We recognize that not all states use a county system but we are currently unable to alter the data to reflect the existing governance structures in all states. We encourage communities within each county of a state to use the Rankings as a starting point to delve more deeply into data that are more relevant for your particular governance structure.
We try to rank all counties or county equivalents with a FIPS code. In 2021, we were unable to rank 61 counties or county equivalents due to insufficient data.
Counties were not ranked if any of the following was true:
- They had a missing value for premature death (this happens when there are less than 20 deaths and the data is suppressed for privacy reasons);
- They had an unreliable value for premature death and no other measures of morbidity were available;
- They had an unreliable premature death value, an unreliable low birthweight value, and no other morbidity measures.
Unreliable measures of premature death are identified when the standard error of the estimate was more than 20% of the estimate value and the measure value is outside last year's confidence intervals. Both missing and unreliable values for premature death show up as blank on your county snapshot. However, advanced users may want to visit our analytic files to understand if their data is missing or unreliable. Unreliable measures of low birthweight are identified when the standard error of the estimate was greater than 20% of the estimate value. Low birthweight data is shown on your county snapshot in all cases where it is available.
Our efforts to increase the number of ranked counties include:
- Measure selection – The Rankings try to find measures that are available for the greatest number of counties.
- Multiple years of data – In several measures, the County Health Rankings use the average of multiple years of data, giving equal weight to each observation year. This allows even small, sparsely populated counties to have a larger sample size to base the measure on.
- Modeled data – Some measures, including adult smoking, obesity, and children in poverty, are based not only on survey response, but depend on statistical modeling techniques that improve the precision of the estimates.
These strategies allow us to rank some units that we might otherwise not be able to rank.
Ranking within states
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. The goal of the County Health Rankings, coupled with data comparability and availability issues across states, means that we can only provide county rankings within states.
However, if you wish to compare counties across the nation, we have prepared guidelines to describe which measures can be compared across states.