But I thought The Onion was supposed to be satire:

In a surprising refutation of the conventional wisdom on opinion entitlement, a study conducted by the University of Chicago's School for Behavioral Science concluded that more than one-third of the U.S. population is neither entitled nor qualified to have opinions.

Seriously, though, I was just reading Richard Wiseman's book Quirkology, which has a chapter on what makes a good joke. And he points out that the best jokes "create a sense of superiority in the reader." This one is cleverly turned because there's no out group. Everyone thinks they're part of the 62%, just as everyone thinks they are a better-than-average driver.