[dragonwriter]

Disability determinations are based on your usual work before the injury/condition on which disability determinations are based, not just the condition you have -- so the particular industries dominant in a region may have a very large impact on disability, not just because of the particular health risks associated with the industry but because of the kind of health conditions that will make someone disabled for the kind of work being done. (Also, changes in economic conditions can cause those able to work to move out to where the work has moved to -- and not be replaced, as the absence of work fails to draw new people in -- resulting in a disproportionate share of unable-to-work left behind.)