On TradeSports around April 2006, the implied probability of a US or Israeli attack on Iran before December 2006 was about 20 percent.

Judge as of 2006-04-10. True: TradeSports (or the closely linked Intrade) prices in roughly early to mid April 2006, for a contract on a US or Israeli air strike or attack on Iran before the end of 2006, traded at about 15–25 (i.e. an implied probability of about 15–25%). Mostly true: the price was about right but the contract's exact terms differed slightly (e.g. US-only, or a different end date close to December). Mixed: the price was roughly in range only at times, or the contract only loosely matched. Mostly false: the price was clearly outside about 15–25% but a similar contract existed (e.g. at 10% or 35%). False: there was no such contract, or prices were far from 20%.

Set before the research began.

1. E1 A mini-interview with Dr. Robert Hanson, crowd prediction data expert George Mason University (Robin Hanson's press page; article by Steve Peterson) · 4 April 2007

   “Apparently, Tradesports users were less concerned about potential military action against Iran since they collectively wagered a 20.5% chance that an air strike would occur by the end of this year.”

2. E2 Policy Analysis Market - Wikipedia Wikipedia

   “One, Intrade, had previously offered futures on events such as the capture of Osama bin Laden, the US Presidential Election, and the bombing of Iran.”

E1 is an independent reporter's account on Robin Hanson's press page. It says Tradesports users put a 20.5% chance on an air strike against Iran by the end of the year. That price sits inside the 15–25% range. The page's file name points to April 18, 2006, but its listed date is 2007-04-04, so the timing is not fully settled. The quoted contract is about an 'air strike against Iran' and does not say it covers a US or Israeli attack. E2 confirms that Intrade ran contracts on bombing Iran. Because the price matches but the date and exact contract terms are uncertain, the verdict is mostly true rather than true.