The size of the keyrings of global PGP servers is knowable. I don't have a link to the analysis from which I draw the numbers, but the summary is about 100k PGP

The size of the keyrings of global PGP servers is knowable. I don't have a link to the analysis from which I draw the numbers, but the summary is about 100k PGP keys. Take into account unusable keys and duplicates, and some number in the (probably high) tens of thousands is a reasonable estimate for PGP users. In terms of anecdata, the only people I've known to have used PGP where the ones working on supporting it in the email client; I've seen more evidence of S/MIME email than PGP, and even that is extremely thin on the ground.