Analyst Black Ops 2 sales a 'cause for concern,' downgrades Activision
Zooming in on yesterday's NPD data for November, it turns out Call of Duty: Black Ops 2 sold 7.5 million copies in the United States. The retail tracking service also told Gamespot that second-place entry Halo 4 sold 3.2 million units, while runner-up Assassin's Creed 3 moved 2.9 million copies.

NPD's data tracked Black Ops 2 sales from launch on November 13 until November 24. The game would go on, according to Activision, to reach sales of $1 billion four days later.

This article was originally published on Joystiq.