That’s a hell of a graph.
But also not unusual.
This is what I do. My approach to SEO is entirely based on what we know the search engines want us to do. I don’t try to trick them or do anything that’s going to harm your rank down the line.
By matching Google’s ethos I can plan ahead, making sure changes they make improve your ranking.
This graph shows the impressions (number of times appearing in search results) of one of my recent clients. The dotted line is before I did any work with them. The solid line starts when I delivered their SEO – and you can probably tell for yourself the date when Google first reindexed the site afterwards.