There are many misunderstanding about the duplicate content and duplicate PAGE. They are not the same thing. It is so clear that the duplicate content is that the content around 70% same will be considered copy. But the Duplicate Page is the meaning that use the SAME HTML way to show the content. So here is the theory about it. Some websites owner scrape the same content to build the website, but google still index them, WHy this happen. Cuz the basic theory is , google read the page use the HTML way, and you can use different way show the same content.