NEW YORK (CNN/Money) - The Patriots' Super Bowl 32-29 win might be good news for New England sports fans, but it'll probably make superstitious investors pretty nervous.

That's because the Super Bowl stock indicator, admittedly not a sound portfolio management tool, holds that a victory in the big game by teams from an old American Football League team means the bears will be on the prowl.

After a better than 90 percent success rate the first XXXI years of the game, the indicator has had a rougher record in recent years. Unfortunately the one year since the 1997 game that is was clearly correct was 2002, when the Patriots' first Super Bowl victory was followed by a 30 percent drop in the Standard & Poor's 500 index that year.

Of course it's safer to be wandering around the line of scrimmage without protective gear than it is to base investment decisions on the outcome of a football game. But that doesn't stop the football fans who populate the brokerages firms of Wall Street from talking about the indicator.

"Wall Street has a lot of football fans," says Jeff Hirsch of the Stock Trader's Almanac. "The Super Bowl indicator might be fun, but I'd put more credence into astrologic market predictors. Any correlation between the stock market and the Super Bowl that can be dug up is just coincidental."

For the first XXXI years of the game, it was right XXVIII times, or 90.3 percent of the time. But it's been in a slump since the 1997 game -- the type of slump bad enough to get an NFL coach fired.

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The last two years of the last bull market -- 1998 and 1999 -- followed victories by the old AFL Denver Broncos, while start of the bear market in 2000 followed a victory by the NFL-born St. Louis Rams.

Last year's winner, the Tampa Bay Buccaneers, was created in 1976, and played its first season in the AFC, the successor to the AFL. But it has spent all but that first year in the NFC, as was the plan when it was created, so it clearly has an NFL flavor to its history.

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The key though, it seems, is that the Tampa Bay beat an original AFL team, the Oakland Raiders. In 2001, a negative year for stocks, the Baltimore Ravens beat an old NFL team, the New York Giants.

The Ravens team was created by the move of the old NFL Cleveland Browns, but the NFL has ruled that the Ravens are a new team, while the expansion Cleveland Browns count as the original NFL team in terms of franchise records.