Since November 22nd we have been noticing a new trend with how Google applies algorithms to detect bad links. Earlier in 2012 the focus was very much around major penalisations where a site would literally disappear overnight for lots of keywords but the trend across November, December and January is very much about Google reducing the rankings of certain sites gradually week after week.
We all know that Google has algorithms to detect bad links and the evidence of this was very visible earlier in 2012 but with this latest change Google seems to have developed the capability to continually detect and devalue bad links as part of the standard crawl process, something they were never very good at before. The net result of this is that as Google completes a crawl of a website and the sites linking to it they can devalue those links in real time rather than waiting to roll out a major update such as Penguin or a manual link penalty.
A lot of sites that are suffering are ones that may have been penalised before due to bad links and have not yet removed them all but there are some that are losing ground from a strong position which indicates the latest change is not confined to sites that were hit in the first half of 2012. Google has made it clear that the disavow tool works on a crawl basis whereby all sites submitted will be crawled before the link weight can be cancelled out so there is every reason for them to have merged this capability with the “bad site detection” algorithms they already have in place.
Realistically Google has to move towards a continual process because manual penalisations are not scalable in the long term and they much prefer algorithms over people.
Below are some examples of this trend as shown on Searchmetrics for some of the several hundred sites we monitor recently as part of our competitor analysis. There are lots more that we have seen similar patterns for.
I have only included the past few weeks data rather than the full year because I didn’t want to identify any sites in particular. We would be interested to hear from you in the comments if you have noticed any sites on a gradual slide recently and whether they had previously been penalised or not?