In addition to PepsiCo and Nike, the study tracked the performance of seven additional publicly traded sponsors: Accenture ( ACN); American Express ( AXP); AT&T ( T); Electronic Arts ( ERTS); Procter & Gamble ( PG); TLC Vision ( TLCVQ); and News Corp. ( NWSA).

News Corp. owns Golf Digest; Gillette is owned by P&G; Electronic Arts offers the Tiger Woods PGA Tour Golf game.

Overall, the UC Davis study concluded that the scandal reduced shareholder value in the sponsor companies by 2.3%, or about $12 billion, a finding that the authors said cannot be explained away by typical daily variation in stock performance.

Not surprisingly, the three sports-related companies, Electronic Arts, Gatorade and Nike, fared the worst, experiencing a 4.3% scandal-generated drop in share value. That percentage drop equals a stock market handicap of $6 billion.

Accenture, one of the first companies to drop Tiger Woods -- and a company that is not sports-specific -- experienced no ill stock market effects from the scandal.

"Nike and other premier sports-related sponsors are special for an athlete like Tiger Woods," the UC Davis finance professors explained. "They are themselves powerful brands that add value to Tiger's brand and create other financial opportunities for him. This gives a premier sports sponsor the bargaining power to capture some of the profits generated by an endorsement deal with Woods -- so that if the Tiger brand is tarnished, those profits may decline."

While the pace of losses had slowed by Dec. 11 -- the day Woods announced his leave from golf -- the study found that by as late as Dec. 17 shareholders had yet to reverse their losses.

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