The lightest gamblers—the 10% of customers who placed the fewest wagers over the two years—also had the highest winning percentage. About 17% of them ended up in the black—tough odds but still better than the dismal 5.4% winning percentage of the heaviest gamblers. - Mitchell Tsai

Among the whole group of 4,222 gamblers, just seven won more than $5,000 (€3,698) over the two years, while 217 lost more than $5,000. That's a 31-1 ratio of big losers to big winners. - Mitchell Tsai

Poker is partly a game of skill, and the outcomes reflect that. About one-third of the poker players classified as "most involved" by the Harvard researchers ended up winning money over time, while just 10% of the rest ended up in the black. - Mitchell Tsai