There is no broad reaching research. Everything I know of is regional. Probably around fifteen percent if I were to hazard an educated guess.
Maybe higher, if you count women in dope houses using meth to buy a younger person to make them feel young. You will hear testimonies of that behavior in twelve step programs and the women who do it seldom connect the reality that since the young guys wouldn’t spend a moment naked with a woman their mom’s age unless she were providing the drugs means that it is pretty much the same as if she were paying cash.
I think 15% is way too high, but let's work with that. 85% of $3.1 million is $2,635,000. That is $2,635,000 that could have helped cash strapped MRAs or prostate cancer researchers, but made abusive pimps rich instead.
Getting back to my original point, can you explain the logic of male thinking that would have so many men patronize these pimps' "products" to the tune of $2,635,000, instead of supporting the MRAs and prostate cancer researchers who are trying to help them?
With that in mind, here's something for your perusal.