How many caves are on private lands that are not currently and may never be open to cave diving due to owner's fear of liability?
That is a good question, but I'm not sure how keeping the IUCRR reports secret helps that.
Perhaps what we need is more data. Start collecting how people cave dive are conducted each year compare it to medical and non-medical accidents.
I am willing to bet that number is quite low. I don't know of how many medical events we have in cave diving. As those are even more hush hush. We seem to get about one cave diving accident every year to two years.