Last month's NPD figures were rather disappointing, reflecting a 15 percent decline in year-over-year sales. With the exception of Red Dead Redemption and Super Mario Galaxy 2, it appears gamers simply aren't buying as many games as they used to ... and, predictably, Wedbush Morgan analyst Michael Pachter has a theory.

The problem? Online games. According to Pachter, "the overall decline was due to a very large number of people playing multiplayer online games." With an estimated 12 million players spending 10 hours a week rampaging through Activision's shooter, Pachter argues that online games like Modern Warfare 2, Halo 3 and Bad Company 2 have "sucked the available time away from what otherwise would be spent playing newly purchased games."

While there are many other factors to consider -- the still-sluggish economy, the declining sales of key Wii software (a la Wii Play) -- Pachter's point does seem to have some merit. Unfortunately, his publisher-centric solution is unlikely to win him many fans among gamers. The "monetization of multiplayer," as he describes it, would have publishers figuring out some method to charge gamers to play online. It's a risky proposition that could bear some terrible consequences, but the current model is, as Pachter puts it, "devastating for publishers and shareholders, who are seeing sales and profits decline."

This article was originally published on Joystiq.