DAVIS, Calif. ( TheStreet) -- Add Tiger Woods to the list of factors that need to be modeled into equity risk algorithms. A new study from University of California, Davis finance professors estimates that shareholders of such Tiger Woods-endorsed stocks as Nike ( NKE) and PepsiCo ( PEP) -- which makes Gatorade -- have lost between $5 billion to $12 billion in market value since the Tiger sex scandal broke. Not even the best golfing clinic could correct that hefty share price slice. While much of the focus in the aftermath of Tiger's sexual bogey has focused on the massive hit to his unprecedented endorsement earnings, the UC Davis professors have quantified a loss to shareholders in these Tiger-endorsed stocks that would equate to decades' worth of Woods' personal endorsement income. Victor Stango, a professor of economics at the UC Davis Graduate School of Management, and co-author of the study along with economics professor Christopher Knittel, 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 the golf great announced his indefinite leave from the sport. The UC Davis economists compared returns for Woods' sponsors during this period to those of both the total stock market and of each sponsor's closest competitor. They also reviewed returns for four years before the car accident to determine how each sponsor's market performance normally correlates with that of the total market and of competitor firms.