"The size of key gamer segments are shifting, with mobile gamers now representing the largest gamer segment, edging out core gamers, which was the largest segment in 2011," NPD said in a release.
Ranks of US videogame players decreased by nearly 12 million, or five percent, from last year to 211.5 million, according to a "Gamer Segmentation 2012 The New Faces of Gamers" report.
"Given the long life-cycles of the current (videogame) consoles and the increasing installed base of smartphones and tablets, it's not surprising to see a slight decline in the core gamer segment," said NPD analyst Anita Frazier.
"It's the revenue contribution of the core gamer segment that continues to outpace all other segments and remains vital to the future of the industry."
The number of "mobile and digital gamers" grew while the other five segments of the market measured in the NPD report registered declines. Other gamer categories included personal computer gamers and families.
"Looking across the total gaming audience, we see a tremendous impact from mobile gaming, particularly on smartphones and tablets," said Frazier.
NPD reported that the percentage of gamers who played mainly on smartphones or other mobile devices grew from nine percent to 22 percent of US gamers, while the core gamer group slipped to 21 percent of the total.
A separate "digital gamers" category was comprised of players that use the gamut of hardware from personal computers and consoles to mobile gadgets but who acquire content online in forms such as applications or software downloads.
Ranks of digital gamers grew four percent to become 16 percent of the overall population of US players, and members of that group were the most voracious when it came to acquiring games, according to NPD.