NEW YORK (CNNMoney.com) -- Investors scored big Sunday when the New York Jets lost to the Indianapolis Colts -- at least according to the Super Bowl stock indicator.
Here's how it works. If a team that had its roots in the National Football League wins, the Dow Jones industrial average should go up. If a team from the upstart American Football League wins, stocks should go down.
The AFL merged with the NFL soon after Super Bowl III, when the AFL Jets upset the then-NFL Baltimore Colts.
In the 43 years the Super Bowl has been played, the indicator has been correct 81% of the time. That includes last year's game, when the win by the Pittsburgh Steelers correctly predicted the rebound in stocks before many investing professionals were willing to go out on that limb.
The two NFC teams playing this Sunday -- the Minnesota Vikings and the New Orleans Saints -- both have NFL roots. So the stock market had to dodge only a Jets win.
Of course basing investment decisions on the outcome of a game makes as much sense as playing football without a helmet. But according to a study by George Kester, a business professor at Washington & Lee University in Lexington, Va., an investment strategy driven by Super Bowl results has done quite well.
If you'd moved into Treasury bonds following wins by former AFL teams, and back into stocks following victories by teams from the old NFL, you would have performed more than twice as well as buying-and-holding an S&P 500 index fund over the same period.
Kester said while he doesn't believe the indicator is a wise way to make investment decisions, the better return on the Super Bowl-driven fund was "a result that would be the envy of many portfolio managers."
Of course, the Super Bowl indicator has been wrong eight times, often spectacularly so.
The New York Giants' upset win in 2008 over the New England Patriots was supposed to bring about a bull run for stocks. Instead the Dow crashed 33.8% that year as the credit markets and banking sector imploded.
Similarly, the back-to-back wins by the Denver Broncos, formerly of the AFL, in 1998 and 1999 did little to slow the rising bubble in tech stocks. The market didn't cool off until 2000 -- after the St. Louis Rams, a team with its origin in the NFL, won the Super Bowl.
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