A new study suggests that using phones to play video games is becoming more popular – it’s  a trend that’s causing a shift in the US gamer landscape.

The new NPD Group study found that 71% of US gamers use their phones to play video games, up 4% from 2013. It was the only type of gaming device to have grown in use from 2013 to 2014.

The study also identified the types of gamers contributing to the trend.

The Avid Omni Gamers, defined as those who play on multiple systems, was also the only gamer segment to grow in 2014. The multi-system players segment grew by 6%  to encompass 22% of the total gaming population. It replaces Casual Gamers as the second-largest gamer segment. The largest segment for 2014 is Free & Mobile Gamers, who account for 29% of gamers.

Both Avid Omni Gamers and Free & Mobile Gamers reported phones as their top system/device for gaming in 2014. The PC continues to lead among Casual Gamers and Social Gamers, while the console took the top spot among Core Console Gamers and Family Gamers.

In terms of sales, the study found that gamers spent an average of US$48 in the past three months on physical game cartridges. This compares to spending an average US$16 on digital games for the same time period in 2014.

The good news is that spending for all gaming categories is on the rise:  last year, gamers spent US$45 on physical games, and US$11 for digital games for the same time period.

Core Console Gamers and Family Gamers both reported buying more physical games than digital games. In tandem with the amount of money spent on games increasing, the amount of time spent playing games also rose. The study found that gamers on average are spending more time each week playing games.