Moz have released the analysis of all the Google Search Engine ranking factors this week for 2013. Moz has extracted data from all the top SEOs in the UK, USA, France and worldwide and has correlated this information. Moz, the real authority on SEO said: 'We gather this data to gain insight into the factors that may help—or hurt—a website's visibility in search engines".
The report shows that Relevance is in line with SEO strategy for its clients especially their early dedication to the G+ social media which has come out 2nd in importance in a list of 100s of factors (read Rumble Romagnoli's article on how G+ would be vital to the Google ranking algorithm in 2013 going forward.)
The report also shows why companies require SEOs: the algorithm is constantly changing, and in-house people might not be so up-to-date with these changes, and the algorithm is so complex and there are so many affecting factors for the Google algorithm that most companies would need SEO agency help.
Please see the table and analysis below from Moz - thanks guys.