By Martha Heberlein

I know I’ve said it dozens of times – states are different. Like people themselves, they have their own characteristics, quirks, and personalities that make them unique. But what about within states – are there differences of note? Why, of course (I’m sure we can all think of a long list of differences between, say New York City and upstate NY). And lucky for us, a recent data release from the Census highlights how health insurance coverage varies within states’ very own borders.

(Quick methodological note for those of you who are interested in such things: the Small Area Health Insurance Estimates (aka SAHIE) are model-based and combine data from a variety of sources. These data represent coverage in 2007, prior to the economic downturn. They are currently the Census’ only data source on health insurance for every county in the US. For more on the various measures Census has on health coverage, check out this helpful fact sheet. The Census also computes small area estimates for income and poverty (aka SAIPE).

Now back to the data at hand – at 26.8%, Texas has the highest rate of uninsured in the country. But where are those 5.8 million folks living? The range in the uninsured rate is quite wide, from 16.6% in Collin County to 49.5% in Kennedy County. What makes these two counties in the same state so wildly different in terms of health coverage? A quick look at some demographic data provides us some idea:

Collin County, located just north of Dallas, is about 850 square miles and has about 765,000 people. In 2007, the median household income was around $80,000.

Kennedy County is located on the Gulf Coast between Brownsville and Corpus Cristi. It’s almost twice the size of Collin County, 1,450 square miles, but has less than 400 residents, with a median income of about $30,000 in 2007.

I think it’s fair to say that we don’t have to pick on Texas as an example, as other states are bound to have within-state variation (even Massachusetts – known for its low uninsured rate of 7.8% – has a range of 6.6% to 13.9%).

State officials and advocates should find these data very helpful in identifying which areas of their states have the greatest number of uninsured residents and possibly understanding the reasons for such differences. (Note – although I didn’t do it here, you can also look at the data by age ranges and income levels). And when making the case for targeting outreach efforts, both for those who may already be eligible for coverage through Medicaid and CHIP and, in 2014, for those who will become newly eligible, having data to support your claims will make your case that much stronger.