Anyone using the Google Search Engine knows that almost always results from Wikipedia.org are among the top 10 Search Engine Results Pages (SERPs).  Some people say over 95 % of Wikipedia Pages, rank in Google’s Top 10 for most keywords.

As you know the aim of Link Popularity, is to increase the number of incoming links to your Website.  One of the most important factors that the Search Engines consider while ranking your Website is the number of Incoming links to your Website.  i.e., the more incoming links to your Website, the better.

This led people to Spam different Websites, especially Websites having User generated Content(UGC) — for example, Wikipedia.org  — in pursuit of increasing Incoming links for their Websites.

In order to fight the above Search Engine Spam Google introduced the NoFollow tag in the year 2005 . This Tag was later recognised by some other major Search Engines over a period of time.

The NoFollow tag (rel=”nofollow”) is an HTML tag that tells Search engines to bypass the link during indexing. i.e.,   if  a link has an  NoFollow tag (rel=”nofollow”) , that does not add to Search Engine rankings for the website.

For example,  Visit my  <a href=”http://www.example.com/” rel=”nofollow”> Shopping </a> site.

To fight Search Engine Spam, Wikipedia also added the <rel= “nofollow”> attribute to all outbound links in Wikipedia.org .

Since all the Outgoing Wikipedia links have no NoFollow tag (rel=”nofollow”) ,  it is same as not having Outgoing links at all for Wikipedia.org . However, there are millions of Incoming links for Wikipedia.org.

So, the ratio,
Number of Incoming links/Number of Outgoing links

Becomes very very high… bordering to infinite.

It is for this reason, Wikipedia.org pages are among top 10 positions for most keywords in Google.  There is no other Website in the planet, that can match (or have more) the above ratio as in case of Wikipedia.org.