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Small Area Health Insurance Estimates (SAHIE)

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Small Area Health Insurance Estimates (SAHIE)

Interactive Map Tool


The SAHIE interactive map tool is a Flash-based tool for data visualization purposes. This map tool is intended to deliver more dynamic and interactive content and provide a better end-user experience.  To view this application your system must have the Adobe Flash Player version 10.x or higher installed and is best viewed using 1024 x 768 pixels screen resolution or higher.
Please download the latest free Adobe Flash player if it is not installed.

Mapping Capabilities

The core functionality with this application is to provide the end-user with an interactive map to display estimates of health insurance coverage, or lack of, as thematic maps.  Estimate maps for each geographic level (state and county) and demographic group (age, race, sex, and income categories) are classified and colored dynamically using an equal interval algorithm.  The interactive components are comprised of mouse over tool tip windows to display contextual information, dynamically linked tabular data, navigation tools to zoom in and zoom out, and multiple background images such as satellite imagery, street maps, and elevation to overlay census data and geography.

Boundary Limitations

Cartographic generalization was applied to simplify and smooth line work; therefore, shapes may not represent exact boundaries. 

Data Sources

Census boundaries:

U.S. Census Bureau's TIGER database

Health Insurance Coverage Estimates:

U.S. Census Bureau, Small Area Health Insurance Estimates (SAHIE) Program


The application was developed using the Adobe Flex 4.0 framework, ArcGIS API for Flex 2.2 and ESRI ArcGIS server 10 on Red Hat Linux.

General User Notes

The accessible data files used in this mapping tool are available at:

Details may not sum to totals and percents because of rounding. The percents were calculated before any rounding occurred.  Rounding error will be more prominent for small counties.

A margin of error (MOE) is the difference between an estimate and its upper or lower confidence bounds.  Confidence bounds can be created by adding the margin of error to the estimate (for an upper bound) and subtracting the margin of error from the estimate (for a lower bound).  All published margins of error for the Small Area Health Insurance Estimates program are based on a 90 percent confidence level.

Health Insurance Coverage, 2005-2013


The Small Area Health Insurance Estimates (SAHIE) derived surface was produced using spline interpolation. A spline interpolation uses a set of values located at specific points, and creates a continuous surface over a given area. In this case, the percent-uninsured population under age 65 is interpolated from the geometric center of counties. 

The applied spline interpolation method constrains interpolation to values inside respective states.  In this way, state surface comparisons can be made. 


The map symbology uses a minimum-maximum stretched color ramp centered on the mean uninsured rate for the population under age 65 for all years. In this way, the color scheme is normalized for all years, so year-to-year changes are a result of changes in the uninsured population, not changes to the symbolized value range. The map symbology allows for quick interpretation of difference from the mean.  Hot colors are above the mean, while cooler colors are below it.

Map Projections:

Contiguous states: US Contiguous Lambert Conformal Conic

Alaska: North America Datum (NAD) 1927 Alaska Albers

Hawaii: North America Datum (NAD) 1983 State Plane Hawaii FIPS 1


Interpolated surfaces create bias where values are calculated across large distances, and should be interpreted with caution; however, the surface illustrates a discernible spatial pattern to health insurance related to local phenomenon. 

Data Sources

Geographic boundaries: U.S. Census Bureau's TIGER database

Uninsured Population Estimates: U.S. Census Bureau, Small Area Health Insurance Estimates (SAHIE) Program

Source: U.S. Census Bureau | Small Area Health Insurance Estimates |  Last Revised: March 17, 2015