Kenny didn't sing about knowing when to hold'em and when to fold'em for nothing ...

Freakonomics | Levitt’s Poker Paper: It’s a Game of Skill:

There's a reason some can make a living at it and others can't. And it's not luck.

Using data from the 2010 World Series of Poker, Levitt and Miles found that high-skilled players earned an average return on investment of over 30 percent, whereas all other players averaged a 15 percent loss. This finding has serious implications on the legality of online poker, as that debate is heavily dependent on whether the game is based on skill or luck.