The rate at which Google featured snippets and Knowledge Graph results are served up in search query results continues to change. While change makes it even more difficult for marketers and publishers to keep up, it’s necessary to stay informed because it helps with the optimization process, according to one consulting firm. 

Google featured snippets, used by the site as a source of information, typically change frequently over time. Analysis from Stone Temple Consulting released Tuesday suggests that Google is undergoing an optimization process designed to improve the overall results. So, the latest analysis looks at the general stability of Google’s featured snippet results.

To measure Google’s rate of change, analysts analyzed nearly 5,000 queries for 124 consecutive days. These queries previously served a featured snippet. The goal was to see how often they changed over time. The analysis shows a change could include showing a knowledge graph instead of a featured snippet, showing neither, or swapping out the source site.

About 2,250 queries served a featured snippet for 100% of the test period. Between 90% and 99% served about 1,000. It then drops to about 250 snippets between 80% and 89%. Some 522 of the queries never showed a featured snippet during this test, though during past studies by Stone Temple Consulting analysts have seen featured snippets on these queries.

Knowledge Graph results were far less frequently shown. Some 4,541 of the queries never served a Knowledge Graph for a query.

Stone Temple Consulting analysts also examined the domains that tend to get the most featured snippets. The top 10 domains for desktop were en.wikipedia.org, biography.com, britannica.com, youtube.com, imdb.com, quora.com, webmd.com, drugs.com, education.jlab.org, and Investopedia.com.

The top 10 domains for mobile were en.wikipedia.org, britannica.com, youtube.com, drugs.com, quora.com, webmd.com, biography.com, investopedia,com, imdb.com, and history.com.

Stone temple Consulting also analyzed the churn for featured snippets. About 425 of the keywords tested never served a featured snippet on desktop, and 888 never served a featured snippet on mobile.

About 1567 of the keywords on desktop used more than one site for returning a featured snippet during the analysis, according to the study.

The keyword phrase “what is day student tuition” showed the most variability. During the course of the study analysts viewed 12 different domains used to provide the featured snippet for this keyword phrase. This keyword also went eight days without any featured snippet.

Marketers can view the analysis and report here.