An examination of data provided by the sales tracking firm NPD reveals that the number of released titles stamped with an M for Mature rating fell 14% in 2007 versus the previous year. Revenue from those sales, meanwhile, jumped from $800 million in 2006 to $1.4 billion in 2007.

Three key titles explain the boost in sales: Ubisoft Montreal's Assassin's Creed (PS3, X360), Bungie's Halo 3 (X360) and Infinity Ward's Call of Duty 4: Modern Warfare (PC, PS3, X360). Together, the games sold a combined 11.7 million units in 2007 across all platforms, accounting for a minimum of $700 million in revenue for the year.

The report suggests that if it wasn't for those three titles, revenue for M-rated games may have dropped below 2006 figures. Only one M-rated title placed within the top 10 of 2006's best-selling console games by revenue: Epic Games' Gears of War, which ranked 7th.

While 2008 boasts some very important M-rated console releases such as Epic Games' Gears of War 2 (X360), Kojima Productions' Metal Gear Solid 4 (PS3) and others, the industry will likely continue to rake in the majority of its revenue from E- and T-rated console titles, which accounted for roughly 78% of sales in 2007.