Hacked Site Algorithm- October 2015
The site which are hacked will get remove from SERP's to improve the quality of the search. The web-masters central blog reported that tremendous amount of site are hacked by spammers and used to engage in abusive behavior , as added malware download, promotion of traffic etc.
Queries affected: Roughly 5%
Panda 4.2 - July 2015
As we know Panda is the algorithm for quality contents. The 4.2 update is the first refresh Google's quality content update since Sept. 2014. Sites having low quality contents will get affected while this refresh should be welcomed by sites that were penalized by Panda4.1 if they have corrected the issue that caused for penalized. This update has taken fewer months to rolled out.
Queries Affected: 2-3 % of English language queries
Google core quality update- May 2015
This update is for overall ranking algorithm itself. Search Engine Land's Barry Schwartz received confirmation from a source at Google on May 19th that "there were changes to its core ranking algorithm in terms of how it processes quality signals.
Queries Affected: Not sure. 22% traffic drop observed
Mobilegeddon - Google Mobile friendly update- 21st April 2015
The key factor of this update is mobile friendliness of websites. This update has added mobile-friendly as an important ranking factor. Adding mobile-friendliness as a ranking signal affects mobile searches internationally, across all languages. This update have an significant impact on search results, while providing better and more relevant data to users.
Queries Affected: Approx 40% for mobile search queries.