Consumers spent about $4.5 billion on all things game related in the second quarter of 2011, up 1 percent from a year ago, according to market researcher NPD.

This data about the overall market gives a more accurate picture of game industry growth than simply retail sales of games, which shrank in the U.S. during the quarter.

About $1.44 billion of that $4.5 billion was spent by U.S. consumers in physical stores on video and PC game software. But another $1.74 billion was spent on content via other monetization means, including sales of used games, game rentals, subscriptions, digital full-game downloads, downloadable extras, social network games, and mobile games. If you add hardware and accessories, the total reaches the $4.5 billion number.

“While the new physical retail channel still generates the majority of industry sales, our expanded research coverage allows us to assess the total consumer spend across the growing number of ways to acquire and experience gaming, including mobile apps and downloadable content,” said Anita Frazier, an analyst at NPD.

NPD has begun tracking the expanded definition of game sales — both physical and digital — to give a more comprehensive measure of sales on a quarterly basis. Those measures will be expanded to include the United Kingdom, France, and Germany in 2012.