NPD is often bashed for omitting digital game sales in its monthly industry statistics, and it appears that criticism was taken to heart as the firm has released new report focused on game downloads. We all knew the digital scene was growing quickly, but based on NPD's numbers, services like Steam accounted for nearly half of the unit sales last year.

It's estimated that 21.3 million full-fledged PC games were purchased online and downloaded in 2009, which compares to 23.5 million physical copies bought at retail. Not only is that 48% of the total unit volume, but it accounts for 36% of dollar sales - a grip destined to tighten as more gamers cave to the easy access and bargain prices of digital outfits. NPD offered a breakdown of the top five frontline and casual digital retailers based on unit share, though no precise data was given:

Top 5 Frontline Digital Retailers
Top 5 Casual Digital Retailers
Steam Big Fish Games
Direct2Drive Pogo
Blizzard GameHouse
EA iWin RealArcade