The source of data is the National Center for Health Statistics published by the Centers for Disease Control and Prevention. Deaths include the underlying cause-of-death codes according to ICD-10: X40–X44 (unintentional), X60–X64 (suicide), X85 (homicide), or Y10–Y14 (undetermined intent). Estimates are based on the National Vital Statistics System multiple cause-of-death mortality files. Age-adjusted death rates (deaths per 100,000 U.S. standard population for 2000) are calculated using the direct method. Populations used for computing death rates for 2011–2015 are postcensal estimates based on the 2010 U.S. census. Rates for census years are based on populations enumerated in the corresponding censuses. Rates for noncensus years before 2010 are revised using updated intercensal population estimates and may differ from rates previously published. In this dataset the estimated values of age groups (16 age-groups) are used to form an interval.
Estimates should be interpreted with caution. This is because there are cases in which they are calculated with a numerator of 20 or less and could be considered unreliable. At the same time because of high number of unresolved pending cases or misclassification of ICD–10 codes for unintentional poisoning as R99. For example, this issue is known to affect New Jersey in 2009 and West Virginia in 2005 and 2009 but also may affect other years and other states.
The values that were initially represented by “>30” were replaced by the decimal number 30.999, in order to preserve the format of values in the “County_Age_Adjusted_Rate_Maximum_Value”. At the same time, for all interval values above 30, there is no corresponding value in “County_Age_Adjusted_Rate_Maximum_Value” to avoid confusion with an interval where all values are equal to 30.999.