Less than 2% of albums released in the US in 2011 accounted for nearly 90% of new album sales

"In 2011, 76,875 albums were released and sold at least one copy in the US, according to stats shared by Nielsen Soundscan.  These releases came from major and indie labels, as well as unsigned artists, as long as they were properly registered and set up with identifiers like UPC barcodes.
That group of 76,875 albums collectively went on to sell about 113 million copies in the US.
Of that total, sales of roughly 100 million, or 88.5%, came from just 1,500 releases, or 1.9% of the release total.
Which means that, roughly speaking, 2% of releases accounted for 90% of new release sales."
Source:  DigitalMusicNews, 12th January 2012