The folks at RankRanger came out with a study around Google's featured snippets that shows that on average a featured snippet from a specific site will only be swapped out with a different site but it is rare for it to be swapped out to a third site. Even more, the dominant URL will show 77% of the time, as opposed to the second URL.
This all means to me that featured snippets and their placements are more consistent than I thought.
I covered this yesterday at Search Engine Land with the title Coveted featured snippet space is more exclusive than you think, study shows.
Here is Mordy's tweet on the study:
When Google utilizes 2 URLs for a #FeaturedSnippet one URL garners more than 75% of the market share!
— Mordy Oberstein (@MordyOberstein) February 21, 2019
When you add a 3rd URL into the mix Google siphons market share off that dominant URL (whose market share shrinks to 65%)! https://t.co/FeLhOWsSDE
cc: @rustybrick #SEO pic.twitter.com/rS5dLIz2xq
Now, don't get me wrong, a 3rd URL can show, the featured snippet in its entirety can disappear also. But this study is pretty interesting.
Google oscillates between two URLs within a given Featured Snippet (a bit under 2 over a 30-day period and a bit over 2 URLs during a 90-day period). The data also showed that over a 30-day period Google made just over two changes to the URL within the average Featured Snippet.One URL clearly takes up the vast majority of Featured Snippet market share, specifically over 77% of it. The second, or "alternate" URL (as will be referred to in this post), is present but 23% of the time during the average month.
Forum discussion at Twitter.