Although some people think 13 is lucky, the superstition is still more frequently feared. In fact, it’s believed that one-third of people think that Friday the 13th brings bad luck. There is a word for people who have this dread because the notion is so widespread: paraskevidekatriaphobia.

On Friday the 13th, people stay home, don’t conduct business, and even postpone weddings and other significant occasions. Some studies claim that it is avoided so frequently that the world economy loses up to $2.4 billion annually. Is that just bad luck for the market, or do people avoid doing business and going to work on that day?