So then the person who uses public information is actually the bigger fool than someone who uses no information whatsoever and just picks a side of the bet. If insiders know that a volcano is going to erupt and offers a 50/50 payout, people who know the historical improbability will bet that is will NOT erupt, thinking it is an easy payout. But there will be some idiots out there that bet that it will erupt based on dumb luck.