Friday the 13th isn't any luckier or unluckier than any other day on the calendar ... knock on wood.

Still, that doesn't stop some poor souls who are certain that the day is going to result in bad luck and bad news.

In fact, a study by the Stress Management Center and Phobia Institute in Asheville, North Carolina, suggests an estimated 17 to 21 million people in the United States are affected by a fear of this day.

The official phobia is called, depending on which shrink manual you're afraid to read, "friggatriskaidekaphobia" (Frigga being the name of the Norse goddess for whom "Friday" is named and triskaidekaphobia meaning fear of the number thirteen), or "paraskevidekatriaphobia."

Either way, just learning to pronounce it is part of the cure.

However, research into the people who suffer a fear of Friday the 13th suggests that these poor souls are so paralyzed by fear that they avoid their normal routines in doing business, taking flights or even getting out of bed.

Although it's not good to let fear dictate your life, it's hard to fault when it gets you one to three additional three-day weekends per year.