Tiger Woods' extramarital affairs could cost you if you hold stock in a company he sponsors or a mutual fund that holds stock in those companies.

A new study — not yet published in a journal — finds the market value lost to companies that had the golfer as a sponsor is already as high as $12 billion.

The estimate is separate from whatever money Woods himself may lose as a result of his missteps. The golfer was thought to make about $100 million a year in endorsement income.

"Total shareholder losses may exceed several decades' worth of Tiger Woods' personal endorsement income," said Victor Stango, a professor of economics at the University of California, Davis and co-author of the study.

Stango and a colleague looked at stock market returns for the 13 trading days that fell between Nov. 27, the date of the car crash that ignited the Woods' scandal, and Dec. 17, a week after Woods announced his indefinite leave from the sport. They compared the stocks to the total market and to competing stocks, plus they looked back four years to get a sense of how the stocks have historically done in comparison to the market and to competitors.

The study focused on nine sponsors: Accenture; American Express; AT&T; Tiger Woods PGA Tour Golf (Electronic Arts); Gillette (Proctor and Gamble); Nike; Gatorade (PepsiCo); TLC Laser Eye Centers; and Golf Digest (News Corp.).

Overall, the researchers figure the scandal reduced shareholder value in the sponsor companies by 2.3 percent, or about $12 billion.

"(This) pattern of losses is unlikely to stem from ordinary day-to-day variation in their stock prices," the researchers wrote.

Investors in the three sports-related companies (Tiger Woods PGA Tour Golf, Gatorade, and Nike) fared the worst, the study found. They experienced a 4.3-percent scandal-generated drop in stock value, equivalent to about $6 billion.

On the other hand, Accenture, a global management consulting firm, experienced no ill effects following the accident.

"Nike and other premier sports-related sponsors are special for an athlete like Tiger Woods," said UC Davis economics professor Christopher Knittel. "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. Our study measures that decline."

The pace of losses had slowed by Dec. 11, the day Woods announced his leave from golf, Knittel and Stango found. But as late as Dec. 17, shareholder had yet to reverse their losses.

"Our findings speak to a larger question of general interest in the business and academic communities: Does celebrity sponsorship have any impact on a firm's bottom line?" Stango said. "Our analysis makes clear that while having a celebrity of Tiger Woods' stature as an endorser has undeniable upside, the downside risk is substantial too.