For additional information about the rationale behind our rankings, see our publications.
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. For the 2018 Rankings, we have switched our county definitions to match the more recent versions that our data sources now use. These changes have affected counties in Alaska, South Dakota, and Virginia. 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 2018, we were unable to rank 64 counties or county equivalents due to insufficient data. Counties were not ranked if they had a missing value for premature death, or if they had an unreliable value for premature death and no other measures of morbidity were available. They were also not ranked if the only measures of Health Outcomes available were an unreliable premature death value and an unreliable low birthweight value. Unreliable measures were identified when the standard error of the estimate was more than 20% of the estimate value.
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 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.