GitHub has been publishing their growth numbers since at least 2016: https://octoverse.github.com/2016/

However, they have reported numbers along rather inconsistent dimensions. Like, historically they've focused on number of repos and users and later PR's and issues, and often catch-all terms like "contributions" which includes all of those + comments etc... but the number of commits alone (which apparently is the main culprit now?) has been mentioned very sporadically. This has made it hard to get a consistent sense of historical growth.

Without any other information, however, it is reasonable to assume that a 14x in commits is the prime candidate for instability. Especially since commits are write traffic, which is much harder to scale than read traffic. Plus every 3 - 5x increase in scale can reveal bottlenecks in your distributed systems that you never knew existed, so they probably have like 2 - 3 "generations" of bottlenecks to figure out!