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Our Model and Methodology
IntroductionRanking MethodologyMeasures, Weights and DirectionMeasures Selection and ChangesData SourcesDisparity Measurement MethodologyThe state health rankings are a summation of select state-level population health measures. Ranks are calculated by state for each measure, ordered by the states’ values, with 1 corresponding to the healthiest value and 50 the least healthy value. Ties in value are assigned equal ranks. Model category and health topic ranks are summations generated to show how a state compares to other states for an entire topic, such as Economic Resources, or category, such as Social and Economic Factors. Overall state ranks indicate how a state compares to other states across all weighted measures in the index.
Overall, Model Category and Health Topic Calculations
The state value for each measure is normalized into a z-score, hereafter referred to as score, using the following formula:
The score indicates the number of standard deviations a state value is above or below the U.S. value. A score with the value of zero indicates a state has the same value as the nation. Scores are capped at +/- 2.00 to prevent an extreme score from excessively influencing the state's overall score.
Summation scores are calculated by adding the products of the score for each weighted measure multiplied by that measure’s relative assigned weight and association with health. Measures without weights are excluded from the overall, model category and health topic calculations. Measures positively associated with population health, such as high school graduation and flu vaccination, are multiplied by 1, while measures with a negative association, such as smoking and premature death, are multiplied by -1. Higher scores are associated with better health, and lower scores are associated with poorer health. The rankings are the ordering of the states according to their overall scores. If a state value is not available for a measure in an edition, the value from a prior edition is used; if no value is available for the prior year, the state’s score for the measure is set to zero. If a U.S. value is not available from the original data source for a measure, the mean of all states and the District of Columbia is used. For model category and measure weights, see Measures, Weights and Direction. It’s important to note that the rankings are a relative measure of health. Not all changes in rank translate into actual declines or improvements in health.
DATA CONSIDERATIONS
Data presented in America’s Health Rankings® reports are aggregated at the state level and cannot be used to make inferences at the individual level. The edition year reflects the year the report was released. The data are compiled from many different data sources and are referenced by the year the data were collected. In some instances, multiple years of data are combined in order to increase sample size and improve reliability of results. Values and rankings from prior years are updated on our website to reflect known errors or updates from the reporting source.