According to the NPD Group, for every five gamers in the U.S. who play freemium games, two of those individuals will purchase in-game content. Freemium, which also falls into the category of F2P or free-to-play, is a sales model where the core content is offered without cost but players can optionally purchase items, weapons, classes, maps and other content which are intended to enhance their experience. 

No sales or revenue figures were given, however this news does seem to indicate that gamers are willing to pony up money in order to customize their characters, gain a competitive advantage or otherwise extend a game. This may be encouraging news for developers flirting with the idea of offering their titles under a freemium model. Just to name a few, many games have done so with great success, including Team Fortress 2 who's revenue increased 12x, Angry Birds, Dungeons & Dragons Online and most recently, Tribes: Ascend.

After surveying 6,416 gamers in the United States, the NPD Group discovered that 53 percent of gamers say they are aware of free-to-play games. 38 percent of all gamers claim to be "currently playing" some type of freemium game while 40 percent admit to paying for optional content to enhance their F2P experience. Only 15 percent of gamers aware of freemium games say they don't play any such titles.

Interestingly, there appears to also be a gender gap. NDP Group discovered that women were "significantly more likely" than men to purchase in-game content. No figures were given.

Despite tales of success, the firm's research revealed that gamers were less likely to spend money after playing a freemium game for more than one month. As a result, it would seem natural to extrapolate that developers should focus on providing fresh content regularly in order to maximize revenue and keep players interested.