Search Engine Ranking Factors 2015

Every two years, Moz surveys the opinions of dozens of the world's brightest search marketers and runs correlation studies to better understand the workings of search engine algorithms. We gather this data to gain insight into the factors that may help—or hurt—a website's visibility in search engines.
This year, Moz surveyed over 150 leading search marketers who provided expert opinions on over 90 ranking factors.

https://moz.com/search-ranking-factors