Google’s head of search spam, Matt Cutts, posted a video today about duplicate content and the effects of it within Google’s SERP.
In the video, the question was asked, “Can having duplicate content on your website affect ranking in Google’s search results?” Matt answered that somewhere 25% to 30% of the content on the internet is duplicate.
When Google sees duplicate content it try to group it all together and treated as if it is just one piece of content. Google does not treat duplicate content as spam, but takes all the content and group them into a cluster and shows the best result for the user.
Matt said if you do duplicate content in an abusive deceptive religious or manipulative way, we do reserve the right to take action.