As predicted by Matt Cutts at Pubcon Las Vegas, authorship mark-up disappeared from roughly 15% of queries over a period of about a month. The fall bottomed out around December 19th, but the numbers remain volatile and have not recovered to earlier highs.
Almost all global flux trackers registered historically high activity. Google would not confirm an update, suggesting that they avoid updates near the holidays. MozCast also registered a rise in some Partial-Match Domains (PMDs), but the patterns were unclear.
Multiple Google trackers picked up unusual activity, which co-occurred with a report of widespread DNS errors in Google Webmaster Tools. Google did not confirm an update, and the cause and nature of this flux was unclear.
After a 4-1/2 month gap, Google launched another Penguin update. Given the 2.1 designation, this was probably a data update (primarily) and not a major change to the Penguin algorithm. The overall impact seemed to be moderate, although some webmasters reported being hit hard.
Announced on September 26th, Google suggested that the "Hummingbird" update rolled out about a month earlier. Our best guess ties it to a MozCast spike on August 20th and many reports of flux from August 20-22. Hummingbird has been compared to Caffeine, and seems to be a core algorithm update that may power changes to semantic search and the Knowledge Graph for months to come.
Google added a new type of news result called "in-depth articles", dedicated to more evergreen, long-form content. At launch, it included links to three articles, and appeared across about 3% of the searches that MozCast tracks.
Google confirmed a Panda update, but it was unclear whether this was one of the 10-day rolling updates or something new. The implication was that this was algorithmic and may have "softened" some previous Panda penalties.
Google's Matt Cutts tweeted a reply suggesting a "multi-week" algorithm update between roughly June 12th and "the week after July 4th". The nature of the update was unclear, but there was massive rankings volatility during that time period, peaking on June 27th (according to MozCast data). It appears that Google may have been testing some changes that were later rolled back.
While not an actual Panda update, Matt Cutts made an important clarification at SMX Advanced, suggesting that Panda was still updating monthly, but each update rolled out over about 10 days. This was not the "everflux" many people had expected after Panda #25.
Google announced a targeted algorithm update to take on niches with notoriously spammy results, specifically mentioning payday loans and porn. The update was announced on June 11th, but Matt Cutts suggested it would roll out over a 1-2 month period.
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 were unclear, but some evidence suggested that Penguin 2.0 was more finely targeted to the page level.
Google released an update to control domain crowding/diversity deep in the SERPs (pages 2+). The timing was unclear, but it seemed to roll out just prior to Penguin 2.0 in the US and possibly the same day internationally.
In the period around May 9th, there were many reports of an algorithm update (also verified by high MozCast activity). The exact nature of this update was unknown, but many sites reported significant traffic loss.
Matt Cutts pre-announced a Panda update at SMX West, and suggested it would be the last update before Panda was integrated into the core algorithm. The exact date was unconfirmed, but MozCast data suggests 3/13-3/14.
Right before the Christmas holiday, Google rolled out another Panda update. They officially called it a "refresh", impacting 1.3% of English queries. This was a slightly higher impact than Pandas #21 and #22.
Google added Knowledge Graph functionality to non-English queries, including Spanish, French, German, Portuguese, Japanese, Russian, and Italian. This update was "more than just translation" and added enhanced KG capabilities.
Google announced an update to its original page layout algorithm change back in January, which targeted pages with too many ads above the fold. It's unclear whether this was an algorithm change or a Panda-style data refresh.
After suggesting the next Penguin update would be major, Google released a minor Penguin data update, impacting "0.3% of queries". Penguin update numbering was rebooted, similar to Panda - this was the 3rd Penguin release.
Google published their monthly (bi-monthly?) list of search highlights. The 65 updates for August and September included 7-result SERPs, Knowledge Graph expansion, updates to how "page quality" is calculated, and changes to how local results are determined.
Exact-Match Domain (EMD) Update — September 27, 2012
Google announced a change in the way it was handling exact-match domains (EMDs). This led to large-scale devaluation, reducing the presence of EMDs in the MozCast data set by over 10%. Official word is that this change impacted 0.6% of queries (by volume).
Overlapping the EMD update, a fairly major Panda update (algo + data) rolled out, officially affecting 2.4% of queries. As the 3.X series was getting odd, industry sources opted to start naming Panda updates in order (this was the 20th).
Google made a significant change to the Top 10, limiting it to 7 results for many queries. Our research showed that this change rolled out over a couple of days, finally impacting about 18% of the keywords we tracked.
After a summer hiatus, the June and July Search Quality Highlights were rolled out in one mega-post. Major updates included Panda data and algorithm refreshes, an improved rank-ordering function (?), a ranking boost for "trusted sources", and changes to site clustering.
In a repeat of March/April, Google sent out a large number of unnatural link warnings via Google Webmaster Tools. In a complete turn-around, they then announced that these new warnings may not actually represent a serious problem.
Google rolled out yet another Panda data update, claiming that less than 1% of queries were affect. Ranking fluctuation data suggested that the impact was substantially higher than previous Panda updates (3.5, 3.6).
Google released their monthly Search Highlights, with 39 updates in May. Major changes included Penguin improvements, better link-scheme detection, changes to title/snippet rewriting, and updates to Google News.
In a major step toward semantic search, Google started rolling out "Knowledge Graph", a SERP-integrated display providing supplemental object about certain people, places, and things. Expect to see "knowledge panels" appear on more and more SERPs over time. Also, Danny Sullivan's favorite Trek is ST:Voyager?!
Google published details of 52 updates in April, including changes that were tied to the "Penguin" update. Other highlights included a 15% larger "base" index, improved pagination handling, and a number of updates to sitelinks.
After weeks of speculation about an "Over-optimization penalty", Google finally rolled out the "Webspam Update", which was soon after dubbed "Penguin." Penguin adjusted a number of spam factors, including keyword stuffing, and impacted an estimated 3.1% of English queries.
In the middle of a busy week for the algorthim, Google quietly rolled out a Panda data update. A mix of changes made the impact difficult to measure, but this appears to have been a fairly routine update with minimal impact.
After a number of webmasters reported ranking shuffles, Google confirmed that a data error had caused some domains to be mistakenly treated as parked domains (and thereby devalued). This was not an intentional algorithm change.
Google posted another batch of update highlights, covering 50 changes in March. These included confirmation of Panda 3.4, changes to anchor-text "scoring", updates to image search, and changes to how queries with local intent are interpreted.
This wasn't an algorithm update, but Google published a rare peek into a search quality meeting. For anyone interested in the algorithm, the video provides a lot of context to both Google's process and their priorities. It's also a chance to see Amit Singhal in action.
Google published a second set of "search quality highlights" at the end of the month, claiming more than 40 changes in February. Notable changes included multiple image-search updates, multiple freshness updates (including phasing out 2 old bits of the algorithm), and a Panda update.
As part of their monthly update, Google mentioned code-name "Venice". This local update appeared to more aggressively localize organic results and more tightly integrate local search data. The exact roll-out date was unclear.
Google released another round of "search quality highlights" (17 in all). Many related to speed, freshness, and spell-checking, but one major announcement was tighter integration of Panda into the main search index.
Google updated their page layout algorithms to devalue sites with too much ad-space above the "fold". It was previously suspected that a similar factor was in play in Panda. The update had no official name, although it was referenced as "Top Heavy" by some SEOs.
Google announced a radical shift in personalization - aggressively pushing Google+ social data and user profiles into SERPs. Google also added a new, prominent toggle button to shut off personalization.
Google announced 30 changes over the previous month, including image search landing-page quality detection, more relevant site-links, more rich snippets, and related-query improvements. The line between an "algo update" and a "feature" got a bit more blurred.