Thread: Can Google detect partial duplication?

Detecting partial duplication in content is part of how Google assesses quality. I think with 40% duplication, it should be o.k.

However, Google is working on detecting "duplicate, overlapping, or redundant articles on the same or similar topics with slightly different keyword variations" and factoring into the websites quality score.

Read more: Official Google Webmaster Central Blog: More guidance on building high-quality sites

How does this work with forums/sites that allow for quoting of other sites and post news?

Generally speaking, I don't this is an issue. Google compares one full web page to another page, so even if there are quotes on a page the entire page will most likely be at least 40 percent unique (as bogart suggests). So, adding content to your page would help.

40% will work but when content found by Google more than 40% duplicate content than may be problem occur for any site.