10 Correlations That Are Not Causations

Super Bowl Stock Market Shuffle
When John Elway and his fellow Broncos won the Super Bowl two years running in 1998 and 1999, the Super Bowl-stock market connection fell apart. Doug Collier/AFP/Getty Images

In 1978, sports reporter and columnist Leonard Koppett mocked the causation-correlation confusion by wryly suggesting that Super Bowl outcomes could predict the stock market. It backfired: Not only did people believe him, but it worked -- with frightful frequency.

The proposal went as follows: If one of the 16 original National Football League teams -- those in existence before the NFL's 1966 merger with the American Football League -- won the Super Bowl, the stock market would close higher that following year than it did the preceding Dec. 31. If a former AFL team won, it would go down [sources: Koppett; Koppett; Koppett; Koppett; Zweig].

From 1967 to 1978, Koppett's system went 12 for 12; up through 1997, it boasted a 95 percent success rate. It stumbled in 1998 and 1999, when AFL alums the Denver Broncos won and the market went up [sources: Koppett; Koppett; Koppett; Koppett].

Some have argued that the pattern exists, driven by belief; it works, they say, because investors believe it does, or because they believe that other investors believe it. This notion, though clever in a regressive sort of way, hardly explains the 12 years of successful correlations predating Koppett's article. Others argue that a more relevant pattern lies in the stock market's large-scale upward trend, barring some short-term major and minor fluctuations, and the fact that an original NFL team won every Super Bowl from 1984 to 1998 [source: Norris].