This section describes the logic behind our ranking system, the weighting scheme we employ, and the measures we use to create the Rankings. For more details, please see our working paper and publications. Details regarding the actual calculations of summary scores and ranks can be found in the section, Calculating Ranks.
The County Health Rankings are based on a conceptual model of population health that includes both Health Outcomes (length and quality of life) and Health Factors (determinants of health). These Outcomes and Factors are broken down into a number of components that are broken down further into subcomponents we call Focus Areas.
Weights for each component in the model as well as appropriate measures were then chosen through a process guided by:
- Review of the literature around the impact of various factors on health outcomes
- Ability for factors to be modified through community action
- Review of America's Health Rankings methodology and indicators
- Availability and reliability of indicators at the county level throughout the nation
- Feedback from a panel of technical experts
There is no one "correct" formula or "true" set of weights that perfectly represents the health of a community. County Health Rankings staff used information gathered from the list above to arrive at a set of easy to understand weights that reasonably reflect the different components and determinants of health. We believe they are reasonable estimates supported by the best available evidence balanced with the availability of health data and interpretability. Additional information is available about the methods used to determine weights (Working Paper on Assigning Determinant Weights).
The Rankings are based on summary composite scores calculated from the individual measures. We calculate and rank eight different summary composites:
- Overall Health Outcomes
- Health Outcomes – Length of life
- Health Outcomes – Quality of life
- Overall Health Factors
- Health Factors – Health behaviors
- Health Factors – Clinical care
- Health Factors – Social and economic factors
- Health Factors – Physical environment
Health Outcome summary score
To calculate the summary score for Health Outcomes, we combined scores for Length of life (50%) and Quality of life (50%). The weights for specific measures were assigned based on relative importance within the factor and considerations of data reliability and availability. Within quality of life, we assign a higher weight to the low birthweight measure since this measure is based on a census of all live births whereas the other measures are based on a survey of a sample of the population.
Health Factors summary score
To calculate the summary score of health factors, the following weights were used: Health behaviors (30%), Clinical care (20%), Social and economic factors (40%), and the Physical environment (10%). Like the Health Outcomes summary score, weights at each level sum to 100%. The weights for specific measures were assigned based on relative importance within the factor and considerations of data reliability and availability.
To see the weights for all measures, click here.
Ranking within states
We only rank counties and county equivalents within their respective 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. Coupling this with data comparability and availability issues across states, means that we 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.