Why Ranks Change

There are many reasons ranks could change. Our data quartiles provide a helpful tool for the comparison of your county to a similar grouping in your state, instead of comparing difference in individual ranks which might not be statistically meaningful. Rank changes should not be used as a metric to measure progress, but rather, another tool in your toolbox to assess the current health of your county. We encourage a focus on the data underlying the ranks, and not the ranks themselves. However, large changes in rank may indicate interesting changes in health for you to explore further.

Ranks can improve or worsen for one or more reasons:

  • Your county experienced health gains or losses: Change in a rank can be due to actual change in the measures that comprise the rank.
  • Other counties experienced health gains or losses: A rank may also improve or worsen not due to change in your own county’s measures, but because of changes in counties ranked just above or below your county within the state.
  • Random variation in measures: Since all measures have some variation (which is why we report error margins), a fluctuation in county rank may be caused by random variation in the measures that comprise the rank.
  • Changes in ranked measures or their methods: Ranks can be influenced by the introduction of new measures or a change in the methods for current measures. For instance, the 2021 Rankings were calculated using the measure High School Completion (American Community Survey) where the measure High School Graduation (U.S. Department of Education, EDFacts) had previously contributed that 5% of the Health Factor rank. This change improves data quality and comparability across states, and also increases the potential for change in Health Factors ranks from the previous year.

To better understand why your county’s rank may have changed from the previous year, the best place to start is by examining the individual measures that comprise the rank. It can be helpful to explore the following:

  • Your county’s measures over time: Are measure values increasing, decreasing, or staying the same? For instance, take a look at the trend graph for your county’s premature death estimate. Is premature death in your county increasing, decreasing, or staying the same? How does your county’s trend compare to the state and national trends? Looking more closely at changes over time in your county’s measures can help you better understand your county’s progress and potential influence on the change in your rank.
  • Error margins associated with your county’s estimates: Another thing to consider is the variation that is expected within each of the measures comprising the rank. Year-to-year there will be some fluctuation in the measure due to random variation. For instance, it is possible to see substantial change in your county’s premature death rate from the previous year, but if the rate is within the margin of error for the previous year’s premature death rate, the change may not be meaningful. Counties with smaller populations are particularly susceptible to this variation.