5. Whilst in Italy, Friday the 17th is considered the unlucky day.
6. Triskaidekaphobia is more common than you might think, affecting roughly 17 to 21 million people in the United States.
7. Many of these people suffer full blown panic attacks, refuse to leave the house and will not buy anything of significance less it be cursed.
8. The phobia affects business. National Geographic reported "it's been estimated that $800 or $900 million is lost in business on this day because people will not fly or do business they would normally do."
9. The origins of the superstition are murky. Friday and the number 13 have been considered unlucky in many cultures since Ancient times. It's theorized the separate superstitions combined into a super unlucky day.
10. One author traced the fear of 13 to a Norse myth wherein 12 gods are having a good-time dinner party in Valhalla when Loki turned up (becoming the 13th guest) and ruined the vibe by organizing the murder of Balder the Beautiful.
11. Another common theory comes from the Last Supper, where Judas was the 13th guest. Judas being the guy that betrayed Jesus.
12. Many high-rises skip the 13th floor, hospitals often won't have a 13th ward, and many airports lack a 13th gate.
13. Roky Erickson's band was called "13th Floor Elevators". He lost his mind, spent significant amounts of time psych ward, and wrote the absolute shredder album The Evil One.
