Ken Wilber writes in “A Spirituality That Transforms”:
I once asked Katigiri Roshi, with whom I had my first breakthrough (hopefully, not a breakdown), how many truly great Ch’an and Zen masters there have historically been. Without hesitating, he said “Maybe one thousand altogether.” I asked another Zen master how many truly enlightened–deeply enlightened–Japanese Zen masters there were alive today, and he said “Not more than a dozen.”
Let us simply assume, for the sake of argument, that those are vaguely accurate answers. Even if we say there were only one billion Chinese over the course of its history (an extremely low estimate), that still means that only one thousand out of one billion had graduated into an authentic, transformative spirituality. Run the numbers… that’s 0.0000001 of the total population.