In the past year, I may have made about... 100 bookings? I'd say about 25%-30% of them gets canceled.
Some agencies cancel much more frequently than the others in my experience. With certain agencies, I think I get cancellations half the time.
Just offering some statistics from my experience. I think I have a decent sample size to guess around 25%
I had a 2 days time frame this year where i got cancelled 4 times. Different agencies and 1 indy. It was almost laughable. Luxury were the one saving my (2) day. So far in the past year i think i used Luxury the most and only had 1 cancellation once but they really got out of their way to make up for it and eventually i managed to see that cancellation from months ago in my last time in MTL. Unless a drastic change they will be my vote for best agency of the year this year.
But my sample from other agency was not that high. Unlike you i don't book 100 time a years. I wish i could LOL. Its more in the 6 to 8 times a year.
Cancellations were pretty high when i started in the hobby in 2009 going 2010. Then Goodgirls happened in 2012 and Mike had set a standard. At the time he had the biggest agency and its not a secret he was very firm in his direction. He wouldn't accept multiple noshow. If someone was unreliable, she would be let go from Goodgirls. Now you could say it may had been his downfall as well as GG didn't last "that long" but for us clients it was really cool. I still miss Mike to be honest. I know he was not popular with everyone and i dunno everything that happened in the background of course, but with me he was always great and if you were a good client not wasting his time, he would be great with you.