Dated January 2011, and covers most home defense and three gun shotguns. http://www.atf.gov/publications/firearms/012611-study-on-importality-of-certain-shotguns.pdf
Actually some of these guns do have a sporting use. if you consider a shooting match sport.
OldFed, how did you post a comment on the ATF website? The study asks to email comments to an e-address with your name and mailing address so they can look up your tax records.