Interpreting Rankings Data
A natural reaction of some readers when looking at charts that rank their state's rates is to seek explanations as to why their state has mortality rates for some causes of death than other states or than the national average. Some may be alarmed that exposure to environmental carcinogens may be responsible when in fact there are several other more likely explanations. The following points should be kept in mind when interpreting these rankings:
- Differences Among Racial and Ethnic Populations: Some causes of death have different rates for different racial and ethnic populations. When comparing rates across states, the racial makeup of the state's population should be taken into account. Although adjustment of rates by race and ethnicity can take such differences into account, presentation of rates for specific racial and ethnic populations (as opposed to statistical adjustment) may be preferable and is more easily understood by a lay audience.
- Variations in Populations and Health Behaviors: Some differences in mortality rates among states may be explained by differences in known risk factors among the populations of those states.
- Variations in Medical Care: Variations among states in medical care factors may also result in differences in mortality rates. In states where higher percentages of the population participate in health screening, more illnesses will be diagnosed at earlier stages. Therefore, the mortality rate without additional information, only tells part of the story.
- Measuring Burden: The importance of a specific cause of death as a public health problem in a state is more a function of the absolute rate of mortality rather than the state's relative ranking in mortality. Also, the true burden of illness on the health care system and economy of a state is determined by the number of people diagnosed not by the rate. The rate is the number of cases divided by the population. Therefore, the observation that a rate in a state appears high relative to other states may obscure the fact that the absolute number of cases is not large.
- Confidence Interval for Ranks of Rates: Ranking health indices is useful for seeing where a geographic area stands in comparison to other areas. However, ranks are inherently random and are dependent on the variability of the rates. Providing ranks and their level of uncertainty (i.e., the confidence intervals) together demonstrates not only the variability of that area's rate but also the variability of closely ranked areas' rates. CI*Rank presents ranked, age-adjusted mortality rates by state, county, and special region in the US. The site also presents confidence intervals for those ranks.