US videogame fans are spending billions of dollars on digital content and play without setting foot in real-world retail shops, according to figures released on Friday by NPD Group.

An estimated 2.6 billion dollars to 2.9 billion dollars was spent in the first half of this year on game content or play in "non-traditional" venues including smartphones and online social networks.

A first-ever "Total Consumer Spend" report by NPD factored in sales of videogame software downloaded online as well as mobile phone applications, game rentals, subscriptions, and used titles.

Industry tracker NPD is striving to adapt to an evolving videogame market being shaped by hot trends such as "social play" at Facebook or other online communities and games sold as downloads instead of packaged goods.

Real-world stores still account for the majority of videogame industry sales, but expanding the research allows a "more comprehensive measure of a dynamic and rapidly changing games industry," said NPD analyst Anita Frazier.

Approximately 3.7 billion dollars was spent in US stores on software for games played on videogame consoles or personal computers in the first half of the year, according to NPD.

Figures released on Thursday by NPD showed that revenue from videogame hardware and titles at stores tallied 1.22 billion dollars, eight percent less than the 1.32 billion dollars taken in during the same month last year.

"While industry sales of new physical retail sales show a decline versus year ago, it's important to remember that there is a growing volume of content being sold digitally," Frazier said.

Sales of videogame consoles totaled 383 million dollars, a 19 percent drop from the 472 million dollars logged in September of last year, according to NPD.

The one area in which sales rose was videogame accessories.

Sony's freshly-released Move motion-sensing controllers for PlayStation 3 (PS3) consoles credited for helping drive accessories sales of 180 million dollars, a 13 percent increase from the same month in 2009.

Points cards that can be used for buying digital content at Xbox 360 Live and PS3 online game play networks were the most popular accessories, in that order, according to NPD.

"The success of these items at retail, points to the growing importance of sales via digital distribution," Frazier said.