But game sales have been weak in 2009, even as movie theaters set box office records. What gives?

I’ll let someone else try to explain the movie side of the ledger (although those box office numbers aren’t always what they seem to be). But it turns out that there’s a simple explanation for game slump: It’s that gamers are huddled in their basements playing Grand Theft Auto over and over and over.

Gamers are indeed spending more time playing videogames, say new data from Nielsen. It’s just that gamers aren’t spending more money on games. Instead, they’re playing the games they have, buying used games, and increasingly turning to game subscription services.

Here’s the argument in chart form–you can get a summary here or download the full report here (PDF). Click on the charts to enlarge:

Hours played:

Used games purchased:

Subscription rate:

All of which explains why Best Buy (BBY) and Wal-Mart (WMT) are both getting into the used game business and why Blockbuster (BBI) and GameFly are expanding their game rental business. Now, if you’ll excuse me, I’ve got to get back to my game of Hover Kart.

Credit Suisse analyst Gary Balter explained in a research note today that one reason he has maintained an Outperform rating on GME shares is that the company has dominated the used videogame business; he notes that used games generate 44 percent of the retailer’s gross profits, nearly twice the segment’s sales contribution to the company. Over the last several days, he reports, there have been two attacks on the company’s near monopoly in used games.

On Tuesday, Forbes reported that Toys ’R Us has a pilot program to test the sale of used games in some of its U.S. stores; Forbes noted that the program was first reported in the user forums of a Web site called cheapassgamer.com. Other retailers, including Best Buy (BBY) and Blockbuster (BBI), have previously experimented in the segment, but haven’t made much of a dent.

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