Without control groups the sophomoric bromide "Correlation doesn't imply causation." is the "go to" response of all sophists and renders the task of discovery impossibly complicated by the advocacy of political ideologues.
The likelihood of all counties behaving the same with regard to issuance of county currency is vastly less likely, and the damage less far reaching, than at the State level. I know I don't have to convince you that the same applies in the relative dangers of State vs Federal levels.
As I said: All it takes is for one State to unburden its Counties with respect to county currency transactions, and political economics -- that is the science of political economy -- will be revolutionized.