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Moz has announced the publication of the 2015 Moz search ranking factors study. The study shared a lot of data on correlation and expert interviews, it is the largest they put together yet.
In short, it seems links and anchor text still rank supreme with Google. Things like HTTPS and TLDs have very little correlation. Here is the summary infographic they published, but you can dive into the details over here.
Forum discussion at Google+ and Local Search Forums.
