Tiger Woods costs shareholders $13.5 billion

Two US professors have pinned the loss to shareholders from Tiger Woods' marital infidelity at up to $US12 billion ($13.65 billion).

The University of California, Davis, researchers said the new study speaks to the question of whether celebrity sponsorship has an impact on a firm's bottom line.

"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," said Victor Stango, professor of economics.

Stango and fellow economics professor Christopher Knittel studied the stock market for 13 days after Woods crashed his car outside his Florida home on November 27. Since then, several women have said they had romantic affairs with Woods.

Woods eventually confessed to infidelity and lost major sponsorships.

The UCD economists compared returns for Woods' sponsors to those of the total stock market and of each sponsor's closest competitor, a UC Davis news release states.

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