Replying to @jbm@infosec.exchange
@jbm@infosec.exchange @adulau@infosec.exchange yip! Did something similar earlier this year. It's unfortunately not the same methodology so the numbers aren't directly comparable & its not a deep dive into the broad mass but just the big sites/repos that are unavailable, but if you are interested: https://blagh.nyanbinary.de/posts/counting-or-not-counting-securityfocuscom/
Another data point from 2023 from Tod : https://docs.google.com/presentation/d/1jO7y1WHAUTWZwUl4tP3ZRJT0gvG6KxQklUvsXoM6NF4/edit?slide=id.g2793d2f3e58_2_50#slide=id.g2793d2f3e58_2_50