One SEO professional asked John Mueller during a hangout whether Google keeps an internal logbook of their algorithm updates.
John explained that he is not 100 percent sure on this and doesn’t have a good answer for the SEO professional, which he referred to as “Alan.”
Update: This author has since learned that “Alan” was indeed SEO professional Alan Bleiweiss on Twitter.
John did say that they do try to understand everything that changes over time. It’s also really hard to track sometimes.
These types of projects are approved at some point, and then they launch at another point.
When you examine a URL in order to see changes, it’s hard to track such changes even on their side.
Trying to assess what had an effect on a page’s ranking can be tricky.
Even if there were a logbook of changes, it would be really difficult to turn it into something useful and base any SEO plan of action on that.
This happens at approximately the 38:27 mark in the video.