This Friday some people will be so paralyzed with fear they simply won't get out of bed. Others will steadfastly refuse to fly on an airplane, buy a house, or act on a hot stock tip. It's Friday the 13th, and they're freaked out.
"It's been estimated that [U.S] $800 or $900 million is lost in business on this day because people will not fly or do business they would normally do," said Donald Dossey, founder of the Stress Management Center and Phobia Institute in Asheville, North Carolina.
The full story is here, hat tip goes to BrainPicker, and I am not sure how formal that quantitative estimate is. Note also that some of that business is likely made up on other days, either earlier or later.