As a summer pastime, griping about rising gas prices ranks right up there with backyard grilling.  Summer 2012 was slated to be a nonstop kvetching session: In spring, experts were predicting we’d pay $4 a gallon by season’s end.

Instead, in a repeat of a now common summer experience, prices dropped. Americans were left to grouse about a jump to a national average of just $3.42 for the month of July.

Why do we get this so wrong so often? To answer that, you have to learn how gas prices really work.