I would expect that if you are not in Midland for a job, or own a ranch there isn’t a lot of reason to be there which would support a low unemployment rate.Would also have to wonder if proximity to Indian reservation nera Yuma would drive up it’s unemployment rate.
More likely, its proximity to a wide open border with Mexico and generous federal subsidies which makes sitting on your ass and drawing a government check on this side of the border more attractive than working on the other side.