This article in Mashable shares interesting statistics on geographical difference in click-through rates for Facebook ads, provided by digital marketing agency:
"Facebook users in South Dakota, Tennessee and Colorado click through ads on Facebook at record rates. In South Dakota, Facebook users click on ads at a rate of 174% the national average.
Meanwhile, residents of Vermont, Alabama and Indiana are the least likely to take the bait. In Vermont, the click-through rate (CTR) is 57% the national average."
The differences are not explained. If you ask me, the first what comes to mind is demographics, most likely, education (states with less educated population have higher click-through rates). I also suspect that states with the higher click-through rates are are ealier stages of Facebook adoption (the novelty factor comes in play, hence more clicks). But that is just IMHO.