Stack, Steven
Wasserman, Ira, and Kern, Roger
Social Science Quarterly Vol. 85, Number 1. March, 2004. Page(s) 75-88.

People who have engaged in paid sex (i.e. used prostitution) or had extramarital affairs were three times as likely to have used cyberporn than those who did not.

The connection between prostitution and pornography is well-founded.