Hello, everyone.
You may not have intended to, but it seems like you're asking me two separate questions. So, I'll address both as I hear them...
As far as the witnesses we interview on the show or that show up to town hall, I suspect that about a third to a half of them have perhaps posted their accounts to some organization or individual. Averaging that out is a pretty hard guess, though. You see, at every town hall meeting we invite some witnesses that we or someone we know have dealt with in the past (most are mined from the BFRO database, but they also come from my own database, and some from local bigfooters friends). This way, we are sure to have at least some good witnesses on hand so we can film the show. In addition to that, depending on the format of the town hall, the venue size, the story line of the episode, and other factors, we put the word out publicly in newspapers and other local media inviting witnesses to come to the meeting to share their accounts. Those meetings are fun for me because we never know what we are in for. Maybe nobody will show up, or maybe we'll get 100 attendees, many of whom are actual witnesses (we've had over 45 at one meeting). More often than not, especially as the show's popularity grew, we would get a lot of stories that nobody had ever told beyond their close family (and sometimes not even to them).
An easier question for me to ponder would be "What percentage of people who see a bigfoot go through the trouble of reporting it to a group or researcher?" For that question, I would speculate something close to 1 reported sighting for 100 actual sightings. This comes from not only working on Finding Bigfoot, but also from just living in Portland, OR. A quick check of the BFRO database tonight gave 7 published reports for Multnomah County (where I live), and 27 from Clackamas County (right next door, and where I do most of my bigfooting). That's 34 total. Over the last 9 or 10 years I've lived there, I've easily spoken to over 150 people in town who have shared their bigfoot stories with me, but have never reported it to a bigfoot nerd. Sure, many of them saw the bigfoots in WA, CA, CO, or elsewhere, but this gives us some feeling of how much people share with organizations or groups. It's safe to say that there are plenty of other people in the area who I have not run across that have seen or encountered bigfoots. I think 1 out of 100 is a safe guess... (But just a guess!)
Hope this more or less answers your question!
Thank you all for your positive words here online, and your smiles when I meet you face to face (as sometimes happens)!
Cliff