[Pokey]

ROI = (R)eturn (O)n (I)nvestment. Therefore, it is the ratio between payouts (return) and buyins (investment). A more interesting question is whether ROI is the proper measure of success/failure in a SNG framework. ROI is a way of measuring your expected payout per SNG; multiplying this by SNGs per hour gives a measure of the profitability of a particular type of game.

Illustrative example: according to the FAQ, a "good" ROI on 11s is 25%, but a "good" ROI on 109s is only 10%. Given that 25% > 10%, someone seeking to maximize ROIs would always play 11s instead of 109s. Someone seeking to maximize hourly return, however, would realize that 10% of $109 is $10.90, whereas 25% of $11 is only $2.75, so there is an incentive to move up in buyins despite the lower return on investment.