InTrade users seem to be investing in the belief for a return that coincides with the Masters tournament in Augusta, Georgia, scheduled for April 8-11. However, the odds dropped from 65 percent earlier on Tuesday to 55 percent around midday.
Woods, who is taking an indefinite break from professional golf, has been in hiding since admitting in December that he had cheated on his wife.
The Dublin, Ireland-based InTrade -- which lists contracts on such topics as US troop levels in Iraq, Sarah Palin's chance of being named the Republican presidential nominee in 2012 and whether someone will be charged with the unlawful killing of pop star Michael Jackson -- added the Tiger contracts at the request of members.
InTrade accepts trades on the probability of events. Its markets are priced from zero to 100, with zero meaning investors see no chance an event will occur and 100 meaning it already has happened.
"It's a hugely important subject, particularly for people like Nike and Accenture who may have had sponsorship deals with him," InTrade Chief Executive John Delaney said. "This is a very big economic issue."
Such sponsors as athletic apparel and footwear maker Nike Inc and video game publisher Electronic Arts Inc have reaffirmed their deals with Woods. However, Accenture Plc and AT&T Inc dropped him as their pitch man after he became engulfed in allegations of multiple extramarital affairs following a minor car accident outside his Florida home November 27.
Woods, believed to be the world's wealthiest athlete, was estimated to earn about $100 million a year in endorsement deals before his troubles.
Pro golfers and analysts who follow the PGA Tour have said the sport will suffer from lower TV ratings until the world's No. 1 golfer returns.
Traders do not seem to agree with speculation that Woods may come back at an event before the Masters -- the WGC-CA Championship in Miami on March 11-14 or the Arnold Palmer Invitational in Orlando on March 25-28. A March contract is at just 20.5 percent.
Instead, they seem to be focusing on the Masters, which Woods has won four times. The odds of his return rise to 85 percent for the May and June contracts, 95 percent for the August contract and 96 percent for the September contract.
The purchase of an April contract, which has been the most popular with 1,045 shares traded, on Tuesday cost $5.50 and would pay $10 if Woods returned by the end of that month. The month with second most volume is March, at 414 contracts.
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