It's Friday the 13th: Cross Your Fingers & Knock on Wood

It's Friday the 13th. If you're knocking on wood, clutching your rabbit's foot, and keeping your fingers crossed to get through the day, here's some advice. Don't waste time worrying about black cats, broken mirrors, or walking under ladders. Think about your money.

Donald Dossey, founder of the Stress Management Center and Phobia Institute in Asheville, N.C., estimates the US loses as much as $800 million to $900 million in business today because millions of people are too afraid to fly, hold meetings, or act on stock tips. Dossey estimates some 17 million to 21 million people in the US alone are friggatriskaidekaphobics -- afraid of Friday the 13th.

And more than a few researchers have concluded that there is a correlation between Friday the 13th and stock returns, thus implying that the stock market is affected by superstition.

The general theory is that the stock returns are lower than normal on the trading day before Friday the 13th and higher on the trading day after the 13th. The idea is that many superstitious investors sell during the day before Friday the 13th, and, once the new trading day after the 13th starts, they return to buy stocks.

"This analogy is simple," Finnish researchers Jarkko Peltomaki and Emilia Peni concluded. "If one is afraid of a monster under the bed, one is probably not willing to look at under the bed to realize how afraid of the monster one can be. So, if one fears Friday the thirteenth and owns stocks, one dislikes holding them until Friday and, since no disaster existed, buys them back after Friday the thirteenth."

But there seemed to be little panic in the market in the past few days. On Wednesday, the stock market snapped out of a five-day slump, and yesterday, the Dow Jones industrial average climbed 1.4% to close at 12,986.58. It was the Dow's biggest jump since March 13 and put the average within sight of clearing 13,000 again.

After the market closed, Google reported better than expected earnings and announced it was issuing a new class of nonvoting stock to shareholders. Google rose 0.5% in aftermarket trading.

Bespoke Investment Group, a stock market research firm and money management group, analyzed stock market results from 1945 through 2011. It describes the historical Friday the 13th effect on financial markets as surprisingly good. Overall, stocks have shown an average positive return of 0.03% more than half -- 52.1% -- of the time between 1945 and the present.

On Fridays, the average daily change increases to positive returns 53.4% of the time. And for Fridays that are also the 13th of the month, the average daily change is even more impressive: up nearly 59% of the time. Now, in fairness, that rate has been slipping in recent years. Since 2000, which Bespoke notes "covers a period that hasn't exactly been great for stock market returns," the DJIA has seen an average change of 0.0% with positive returns only 50% of the time on Friday the 13th. But that's still even odds that things will turn out fine today.

While the overall odds look pretty good for an uneventful Friday, the best way to confirm a superstition is to look for events that confirm it. As Thomas Gilovich, a psychologist at Cornell University, has noted, if anything bad happens to you on Friday the 13th, the two will be forever associated in your mind.

So expect to hear some reminders today about October 13, 1989, when the Dow Jones dropped nearly 7% in an event later nicknamed the Friday the 13th mini-crash. Then there was January 13, 1989, when a virus crippled IBM computers all over Great Britain, creating mass hysteria. And don't forget March 13, 1992, when a massive 6.8 earthquake in northeastern Turkey resulted in more than 500 deaths and widespread property damage -- bad news not only to friends and families of the victims, but to investors in insurance companies who were liable for the losses.

But here's the bottom line. With all the really scary things affecting the markets these days, from massive levels of global debt and questionable policies by central bankers to the willingness of a company to pay $1 billion to acquire a startup with 12 employees and no revenue, Friday the 13th is really nothing to fear.