Angry BirdsTwo reports released this week show the continuing growth and potential market dominance of digital and mobile gaming.

The number of Americans who play at least one hour of video games per month has more than doubled over the last three years, increasing from 56 million in 2008 to 135 million in 2011, according to research firm Parks Associates. The majority of these new gamers are “casual gamers,” the firm says, particularly those who play games like FarmVille and Angry Birds on social networks and mobile devices.

“The increase in the number of gamers is impressive because it crosses almost all demographics,” said Parks Associates research analyst Pietro Macchiarella. He adds most of this growth is due to tablets and smartphones usurping the PlayStation 3, Nintendo Wii and Xbox 360 as popular gaming devices. Three-fourths of tablet owners play games on the device, while 57 percent of smartphone users play games.

The ongoing “casualization” of video games is having an impact on the market as well. British research firm Ovum predicts digital game revenues will increase by 16 percent year-on-year in 2011 to reach $24 billion. They say that number will grow to $53 billion by 2016 as more publishers adopt casual-friendly strategies and free-to-play (F2P) business models. Xbox has benefited greatly from a casualization strategy, Ovum says, by using its motion-sensing device Kinect for Microsoft’s Xbox 360 to expose casual gamers to hardcore titles like racing game Forza Motorsport 4. The research firm says this strategy helped Xbox LIVE revenues grow by 19 percent against last year.

“These changes have significant implications for the gaming industry,” Macchiarella said. “This new majority of casual gamers is looking for games with low entry barriers, with limited investments required in terms of dollars and time necessary to learn the game. In addition, the ubiquity of portable devices and Internet access allows more people to play on-the-go, putting pressure on the gaming industry to design games that can deliver a satisfactory experience within these specific conditions.”