January 22/ Panda #24
Google announced its first official update of 2013, claiming 1.2% of queries being affected.
March 14/ Panda 25
Google’s Matt Cutts pre-announced a Panda update at SMX West, while suggesting that it would be the last update before Panda could be integrated into its core algorithm.
May 9/ “Phantom”
In or around this date, there were several reports of algorithm update which was verified through high MozCast activity. Even though the exact nature of such update was unknown, yet many sites had reported significant traffic loss after its implementation.
May 21/ Domain Crowding
Google released an update to control domain crowding/ diversity deep in the SERPs (pages 2+). Although the timing was rather vague, it apparently rolled out immediately before Penguin 2.0 in the US and perhaps all over the world, too.
May 22/ Penguin 2.0 (#4)
After months of speculation bordering on hype, the 4th Penguin update (dubbed “2.0” by Google) arrived with only moderate impact. The exact nature of the changes was unclear, but some evidence suggested that Penguin 2.0 was more finely targeted to the page level.
After years of ‘P’ animal-themed algorithms, Google created history by switching into a new algorithm, calling it Hummingbird. As commented by TechCrunch, the emergence of Hummingbird 1.0 was “the biggest overhaul to [Google’s] engine since the ‘Caffeine’ overhaul 9which focused on speed and integrating social network results into search) and that it affects around 90% of searches”.
February 6/ Page Layout #3
Google reportedly ‘refreshed’ its page layout algorithm, commonly known as ‘top heavy’. Primarily launched in Jan, 2012, it penalizes websites that contain too many ads above the fold.
March 24/ Unnamed update
While major algorithm flux trackers and webmasters volley around 3/24 or 3/25, many guessed that the new ‘softer’ Panda update had already started taking its toll. Even though many websites had reported ranking changes, Google had not confirmed about its release.
May 16/ Payday Loan
Immediately before the Panda 4.0 update, Google managed to update its ‘Payday Loan’ algorithm, which, however, generally targets ‘spammy queries’.
May 19/ Panda 4.0
Google authenticated a significant Panda update that most likely included both algorithm update as also a data refresh procedure. As a result, around 7.5% of English language searches were affected. Even though Google’s Matt Cutts had hinted the date as May 20, it was implemented a bit earlier