Are you paraskevidekatriaphobic? While the word apparently dates from 1992, the phenomenon has a long heritage. According to one source, 17 to 21 million Americans, 8% or so of our population, are affected to one extent or another, and it costs the U.S. economy up to $750 million in lost revenues annually. —Why? —How? The Guardian and Salon also have something to say on this matter.

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Here’s a quiz to see how superstitious you are. Its queries include a number of superstitions I had not even been aware existed.