Lots of research has focused on inbound links to a site, but little has focused on the number of links actually on a page. Many SEO gurus have recently been talking about something they call ‘PR Leak’which seems to be a theory that the more outbound links you have, the more your page rank on Google "leaks" away.
This concept isn't found in the academic papers published by Google, but does seem to be accepted by a majority of SEOs. I decided it was time to take a look at the number of links present on a page and how that number correlates with ranking.
I gathered the results of the queries that were performed last month by myself and three associates. I counted the number of outbound links on the page and tabulated the results against the ranking of theURL in the search results. The tabulated results were then converted into a normalized "ranking correlation".
The resulting graph show the results for groupings of links normalized into a number between -100 and +100, showing the likelihood of being ranked higher/lower. A value of +100 shows that all ten rankings were in the proper order to show that pages of the studied value always rank higher than pages of another value.
A value of -100 shows that all 10 rankings were in the proper order to show that pages of the studied value always rank lower than pages of another value. Numbers in between show the varying likelihood of rankings proportionally between -100 and +100.
Results & conclusion
As you can see from the graph below, the results are very conclusive. Google ranks pages with outbound links much higher than pages without links. The SEOs touting the ‘PR Leak’ theory are simply wrong.
- There was no attempt to isolate different keywords. I merely took a random sampling of the queries performed by myself and three associates during the month.
- This is merely a correlation study, so it can't be determined whether the leading search engines purposefully entertain this factor or not. The actual factors used may be far distant from the factor we studied.