The data seems to be based off an NPD survey: "Data note: The information in this press release is from NPD’s “Annual Music Study,” which is based on online su

The data seems to be based off an NPD survey: "Data note: The information in this press release is from NPD’s “Annual Music Study,” which is based on online surveys of U.S. consumers age 13 and older. NPD conducted consumer surveys between December 14, 2011 and January 3, 2012, and the final reporting is based on 5,799 completed surveys. In order to compare music acquisition across formats, NPD uses an equivalency of 10 standalone digital tracks for each CD album."[0] I would guess they were counting all USB storage devices as "hard drives", so a large percentage is likely just USB sticks. [0] https://www.npd.com/wps/portal/npd/us/news/pressreleases/pr_120306 https://www.npd.com/wps/portal/npd/us/news/pressreleases/pr_...