To compare, the SoundScan-era high for album sales in a single week came in late December of 2000, during the height of CD sales, when 45.4 million albums were sold in the week ending Dec. 24. (To put that figure in perspective, in all of 2013, there were 289.41 million albums sold. But in 2000, there were 785.14 million albums sold.)
It's normal to see soft sales figures in January every year -- as the market adjusts back to normal after the Christmas shopping season, and because there are few new major albums to drive sales. This week's top selling album, for example, is the "Frozen" soundtrack, with 86,000 sold.
While it's now common for album sales to fall below 5 million units in a week, this wasn't always the case.
Weekly volume didn't fall below 5 million in the SoundScan era until 2010, when, in the week ending May 30, album sales dropped to 4.98 million.
In 2010, there were a total of four weeks with under 5 million in sales. In 2011, that number shrunk to just two weeks, but then stepped back up to three weeks in 2012.
In 2013, things got really crazy, when there were 18 weeks where album sales dropped below 5 million.
With this week's sum about 250,000 units away from scraping 4 million, it would seem another low threshold is about to be reached.