More info from Major on his blog
http://news.xbox.com/2014/01/xbox-one-december-npd
December 2013 NPD highlights include:
Total combined retail spend on the Xbox platform (Xbox One and Xbox 360) in December reached $1.39 billion, 50 percent of the combined software, hardware and accessories spend in the U.S. (Source: NPD Group, December 2013).
During the month of December, Xbox One held six of the top 10 spots on the new generation console game title list: Battlefield 4, Forza Motorsport 5, Dead Rising 3, Ryse: Son of Rome, Madden NFL 25 and Call of Duty: Ghosts (Source: NPD Group, December 2013).
Fans continue to show their excitement for new generation Xbox One games,
with U.S. consumers purchasing an average of 2.9 games* per console since launch.