In an 18-month study, the team surveyed 917,410 sexually explicit pictures, descriptions, short stories and film clips. On those Usenet newsgroups where digitized images are stored, 83.5 percent of the pictures were pornographic.
Abstracts discuss methodology in detail.
The fact is, that if you look at .binaries on Usenet, most of them come from adult BBSs. That you think this somehow supports applying your characterization of the contents of Usenet from the contents of commercial porn BBSs shows that a good remedial methods course is in order. Rimm doesn't know either. There's no part of the study that supports this leap. And yelling at me is not going to make that go away.