Virginians love and hate disability benefits, depending on which county you’re in.

The state is simultaneously home to counties with some of the nation’s lowest and highest rates of disability benefit use. Five of the 10 counties with the highest rates are in Virginia, as are four of the 10 counties with the lowest rates. The state is an extreme example, but it’s emblematic of a nationwide pattern: use of disability benefits varies widely even in small areas.

The program is problematic to say the least. In 2012, $120 billion went to 9 million people, some of whom are still able to work. It has spawned what NPR dubbed the disability-industrial complex. And official estimates predict the program’s trust fund will be depleted by 2016.

Geographic differences may hold the key to reform, according to a new Urban Institute analysis. The 10 counties with the highest rates are in the south—Kentucky, Virginia, and West Virginia. The 10 with the lowest rates are in three western states — Colorado, Wyoming and Idaho — as well as Virginia.

But even within those states, there’s a lot of variation county by county. And finding out what drives that variation could help to identify the problems with the program. There’s no clear answer, but the Urban Institute’s Stephan Lindner offers five possible explanations in his post:

Prevalence of disabilities: Disability rates are generally higher in the South and Southeast, creating a higher need for DI in these regions.
Economic conditions: Some of the sharp differences across counties could be a result of economic conditions. For instance, all of the counties displayed in Table 1 have large coal mining industries. As coal prices plummeted in the 1980s and threw the industry in a long-lasting crisis, DI beneficiary rates in these regions skyrocketed.
State policies: Sharp differences in DI participation rates between adjacent states like Kansas and Missouri could stem from differences in state policies for other safety net programs like the Supplemental Nutrition Assistance Program.
Determination of DI applications: Caseworkers in field offices assess that state’s DI applications. We do know that caseworkers often decide about identical claims very differently.
Knowledge about the program: DI is complicated. Knowledge about the program might differ across regions, which could influence application decisions. Evidence that this might be the case comes from the Earned Income Tax Credit, where knowledge about program details differs greatly even across small areas.

Read more:

Check out Lindner’s post, which also has an interactive version of the map above.

Read NPR’s incredible deep dive on the program.

Testimony from the Center on Budget and Policy Priorities’ Kathy Ruffing, in which she argues that demographics are largely behind the program’s explosion in recent years.

CORRECTION: A previous version of this post misidentified the number of possible explanations for the geographic variance. Lindner offers five possible explanations.