...according to a tweet from Google's Distinguished Engineer Matt Cutts.
The first update to the second-generation Penguin algorithm designed to target web spam will affect "~1% of searches to a noticeable degree."
Google Penguin 2.0 went live on May 22 and affected 2.3 percent of English-U.S. queries.
Upon the original release of Penguin, Google's official blog stated:
The change will go live for all languages at the same time. For context, the initial Panda change affected about 12% of queries to a significant degree; this algorithm affects about 3.1% of queries in English to a degree that a regular user might notice.
So those are the facts. Panda affected 12% of queries "to a significant degree." Which means that whatever else was affected was affected to an insignificant to zero degree. Which means that at its most significant affect, 88% of the SERPs stayed the same. Upon subsequent updates the SERPs remained the same between 99.9% to 96.7%.
Those are the facts. The premise of this discussion is not established. Google's rankings are not unstable. I think it's important for the facts to be known.