Google posted a line in the data anomalies support
page about an “update to web search logs analysis” when showing the
Search Analytics report in the Google Search Console. The update was
made on December 14, 2015, and it is said to impact only websites.
Specifically, Google wrote, “this change may increase the total number
of clicks and impressions.”
If you look at your Google Search Analytics report in the Google
Search Console, you will see a vertical update line on the December 14
data. That line links to this update in the data anomalies page. Here is
a picture:
I did ask Google’s Webmaster Trends Analyst Zineb Ait Bahajji about this on Twitter and if it was at all related to the app install button change. She said it was unrelated, explaining that Google is now “logging data differently,” which can impact the reports seen in the Google Search Console.
Google has made these changes from time to time, and it is nice that they document them for webmasters.