We looked into this several years ago and found that most of our users had likely encountered and cached the several most popular versions on CDNs. There was a power law distribution in effect.
In the last five years, the release schedule has slowed, so there was a convergence onto fewer versions in the wild, but at the same time, users were visiting fewer sites that used CDN versions (and fewer sites in general.)
In the last five years, the release schedule has slowed, so there was a convergence onto fewer versions in the wild, but at the same time, users were visiting fewer sites that used CDN versions (and fewer sites in general.)