If you judge by my town:
5 (known) unicyclists / 40,000 people = 0.013%
If you only count really serious unicyclists, though, and consider that about (maybe) 10% of them have registered on this forum, you get about 110,000 unicyclists. It’s not very much.
I was actually considering this a few days ago. It’s certainly less than a percentage point. However, I get a few people who come up to me and mention how they can or could ride one once upon a time. And I’ve taught five or six people to ride, it does spread quickly. I’d still estimate there are no more than 100 people who can ride a one-wheeler in my town of about 200,000 (is that how big it is? I’m not sure anymore). Not many, to be sure.
edit: I’m probably the ‘most serious’ - while a few of them own giraffes, none of them can wheel walk, and none of them practice on a daily basis. That’d be 1/100 unicyclists.
I agree that unicycles happen in clumps. Before I learned to ride, there were no unis in spearfish. Now, there are 7 in my town of about 12,000.
I think it’s growing, though. A club just started a couple years ago in Rapid City, and they took like 15 people to Moab. I think clumps happen around dedicated riders. One person will teach others to ride, and it goes from there.
i guess it depends on the crowd…if it were a crowd at a muni covention then i would say 100 out of 100 but in just regular people… id say maybe 1 in the hundred…maybe even one in a thousand
I live in a small town of about 3500 people, and I’m pretty darn sure I’m the only unicyclist. I’m trying to get one of my daughter’s friends to do it. He was over at my house a while back and I got him on my unicycle and told him how to ride it, and within 10 minutes he was riding it 10 to 15 feet! He’s got the capabilities, thats for sure, but you also have to have desire, and that is what takes work on some people.
ask your teacher, i think a qualification for teacher is youve tried to learn or can and dont have one,
at least at my school
I’m hoping to trigger a Princetown “clump”. I’ve never seen another unicyclist when I’ve been out riding, apart from when I’ve been on a ride with other people. Some of the local youths seem to be gradually moving from just taking the mick towards showing some interest, and a couple of them have tried to ride my 20". So you never know, there might be a unicyclist explosion in Princetown in the next few years 
I don’t believe Roger ever suggested 12% of the population can unicycle. If that’s true there must be some remote part of the country (or world?) swarming with unicyclists, to make up for all the ones who aren’t anywhere I’ve ever been.
Even 1% seems a bit high in my opinion.
a whole lotta peopel can ride for like 10-30 feet… its crazy, ive met at least ten peopel that were like… hey i can ride a unicycle, and they can jumpon mine and ride… its prett cool