WISQARS™ Fatal Injury Mapping Help Menu

2.4 Death Rate Calculation Options

These options allow you to specify how rates are to be calculated. The options include the type of rate (crude or age-adjusted), the level of geographic detail for the rates (statewide or county-level), and whether or not the rates should be geospatially smoothed.

Type of Rate

You can use the radio buttons to request either of the following types of rates:

• Crude rates (the default), which are useful when you want to map the observed statewide or county-level rates.
• Age-adjusted rates, which may be preferred for injuries that occur more often among certain age groups than others. For instance, deaths due to falls are more common among the elderly than any other age group. Age adjustment enables you to compare rates across regions, states, and counties without concern that patterns in the maps might simply be due to differences in the age distributions of the populations in the different areas.

Map Level

The map level controls whether a map shows only whole states or individual counties. For national or regional maps, you can use the radio buttons to set the map level to:

• State (the default), which will result in a map showing only state borders and corresponding statewide rates. Hovering over any state with your mouse will open a pop-up window showing the name of the state and the corresponding rate. You can also drill down to a map showing county borders and rates for any state by hovering over the state and clicking your mouse; you can then hover over the individual counties to view county names and county-level rates. When you drill down to a particular state, the resulting map will always cover a full seven-year period (e.g., 2008-2014) even if the initial map (national or regional) covers a narrower period (e.g., 2012-2014).
• County, which will result in a map showing county borders and corresponding county-level rates. County names and county-level rates cannot be displayed by hovering in national or regional maps.

Notes: When a map of an individual state is generated directly, it will automatically show county-level detail. As with state maps obtained by drilling down from a national or regional map, county names and county-level rates can be displayed by hovering over individual counties.

Geospatial Smoothing

For maps that show county-level detail, you can request geospatial smoothing of the rates (whether crude or age-adjusted). Using the radio buttons you can switch between:

• No smoothing (the default), to produce a map showing rates with no smoothing applied.
• Smoothing, to produce a map showing rates that are calculated using a simple geospatial smoothing procedure that pools data across neighboring counties. Smoothing can sometimes help clarify geographic patterns that may be difficult to see in maps showing unsmoothed rates. For further details, see the section Statistical and Mapping Methods for Rates.

Notes: When a map of an individual state is generated directly, it will automatically show county-level detail. As with state maps obtained by drilling down from a national or regional map, county names and county-level rates can be displayed by hovering over individual counties.

When the total number of deaths used to calculate any particular rate is 20 or less, the rate is considered statistically unstable. At a minimum, an unstable rate will be annotated as such, and in some instances will be suppressed entirely. Suppression variously depends on the geographic level of the map element (county, state, regional, or national) being referenced and the death count associated with the rate. The suppression rules are as follows:

• A county-level rate that is unstable (associated death count ≤ 20) will always be suppressed.
• A state-level rate that is unstable (associated death count ≤ 20) can be displayed (but annotated as unstable) provided that the death count ≥10 (per data privacy rules); otherwise the rate will be suppressed.
• A regional or national rate that is unstable (associated death count ≤ 20) can be displayed without restriction (but will be annotated as unstable).

When running queries for a specific intent and/or mechanism of injury or for a demographic subgroup defined by race, ethnicity, sex, and/or age, keep in mind that many counties may have unstable rates. Some national, regional, and state-specific maps showing county-level rates may therefore indicate that many rates have been suppressed. Further details on the calculation of rates are provided in the section Statistical and Mapping Methods for Rates.

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