Nearly half of gamers play mobile games more than they did a year ago, according to the Mobile Gaming 2012 report from The NPD Group, with 23 percent only playing games on smartphones or tablets.

In addition, 59 percent of the total time app players spend using games is spent on mobile devices.

For 37 percent of respondents the reason for their increased gameplay was the greater availability of free apps, while portability and convenience was cited by 34 percent.

Almost 30 percent of app gamers have either made in-app purchases or upgraded to a paid version of an app after using the free version. The average price app gamers feel represents good value for a paid app or upgrade is US$3.

“Many mobile gaming consumers have grown accustomed to gaming for free, making it essential to find the sweet spot for pricing that encourages purchasing by as many consumers as possible,” said NPD industry analyst Liam Callahan.

Gamers who play mostly on smartphones are less likely to have made an in-app game purchase or upgraded to a paid app than tablet users. The likelihood of making a purchase or upgrade increases as the amount of time spent playing games increases.