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Almost every day， Google introduces changes to its ranking algorithm.
　　Some are tiny tweaks， others have shaken the SERPs badly.
　　This little piece of paper will help you understand the most important algorithmic changes and penalties launched in recent years， with a brief overview and SEO advice.
　　Read or get free paper in PDF format.
　　Are your traffic changes related to the Google update？
　　Let‘s see what each update is about and how to adjust.
　　1. Panda algorithm
　　Issue date： 24 February 2011.
　　Danger： repetition， plagiarism or thin content;
　　User-generated spam;
　　Keyword stuffing
　　2. Penguin algorithm
　　Issue date： 24 April 2012.
　　Danger： spam or irrelevant links;
　　Links with optimized anchor text.
　　3. Hummingbird algorithm
　　Issue date： 22 August 2013.
　　Danger： keyword stuffing;
　　Low quality content
　　4. Pigeon algorithm
　　Issue date： 24 July 2014 （USA）;
　　December 22， 2014 （UK， Canada， Australia）
　　Risk： poor SEO on and off the page.
　　5. Mobile algorithm
　　Issue date： April 21， 2015.
　　Danger： lack of mobile page version;
　　Poor mobile availability.
　　6. RankBrain
　　Issue date： 26 October 2015.
　　Disadvantages： lack of query specific related features;
　　Thin content;
　　Bad UX
　　7. Scoring system
　　Issue date： 1 September 2016.
　　Danger： intense competition for the location of the target.
　　8. Fred
　　Issue date： March 8， 2017.
　　Danger： thin， attached， or AD centered.

There is one more recent update called "Maccabees" .This one seems to have targeted unnatural links, links built through link spam, PBNs, or other forms of black hat link development.