EPEL statistics: EL-7 and EL-6
The above is a 7 day moving average graph of checkins to mirror manager looking for EPEL updates. In general it shows that EPEL has been growing steadily since its inception with some some interesting peaks and dips.
In March of 2017, you see a drop off of EL-5 when CentOS end of lifed it from their mirror manager. I don't know if those clients are still just looking for updates and failing or if clusters all over were shut off. You will notice that the EL-7 growth becomes much steeper than it was before, so I am assuming it is people jumping from 5 to 7. In January of 2018, you see another blip. This shows up in the normal data when the Spectre/Meltdown updates came out. It looks like a lot of hosts may only update every now and then, but they ALL updated on that week.
The big news is that EL-6 is still growing by a lot more than anyone would expect. By this time in its lifetime, EL-5 was beginning to drop off, but it would seem that people are still deploying EL-6 in large numbers. That has made it a lot harder for EL-7 to 'catch' up, but it looks like it will finally do so in the next month or so. I realize that in todays 'move fast and break things' this seems crazy slow.. you can't code RUST on EL-6 or 7 without some serious hacks.. but this is actually a fast paced change in the 'ops' world. [I had to support Solaris 2.5 (release in 1995) in 2007. The system it was running had another 5 years before it was to be end of lifed. To replace it would have required recertifying a large amount of other systems and processes. ]