I would be surprised if 5% of college-completing or comparably-educated adults got it. A vanishingly small percentage of people know anything about formal logic

I would be surprised if 5% of college-completing or comparably-educated adults got it. A vanishingly small percentage of people know anything about formal logic. And of those only some fraction internalized it well enough to be facile with it. If there's one thing more widespread than innumeracy, it's the equivalent wrt syllogistic reasoning.