The numbers tend to be closer to about 0.7% in more recent studies, but I think the issue here is that you’re looking for people who sound a certain way. It’s easy to see people who are amputees, from the obviously missing or prosthetic limb to an altered gait. How many people do you hear speak long enough to pick out a stutter? Probably not a lot. And this doesn’t even account for people who do so covertly, or have figured out how to pass. I’ve personally met a handful, not even counting those in my SLP contacts (which would bias my sample). Went to high school with one kid, had interprofessional development with another (he was actually a med student with a pretty mild one). Let’s say it’s 1%. Yes, that’s still approx. 3.2 million people in the USA, but the USA is huge. Psychopathy affects a similar number of people, and you don’t expect everyone you meet to be plotting to use you like an object.