5. The Effect of
Outbound Links

Since PageRank is based on the linking structure of the whole web, it is inescapable that if the inbound links of a page influence its PageRank, its outbound links do also have some impact. To illustrate the effects of outbound links, we take a look at a simple example.

	We regard a web consisting of to websites, each having two web pages. One site consists of pages A and B, the other constists of pages C and D. Initially, both pages of each site solely link to each other. It is obvious that each page then has a PageRank of one. Now we add a link which points from page A to page C. At a damping factor of 0.75, we therefore get the following equations for the

PR(A) = 0.25 + 0.75 PR(B)
PR(B) = 0.25 + 0.375 PR(A)
PR(C) = 0.25 + 0.75 PR(D) + 0.375 PR(A)
PR(D) = 0.25 + 0.75 PR(C)

Solving the equations gives us the following PageRank values for the first site:

PR(A) = 14/23
PR(B) = 11/23

We therefore get an accumulated PageRank of 25/23 for the first site. The PageRank values of the second site are given by

PR(C) = 35/23
PR(D) = 32/23

So, the accumulated PageRank of the second site is 67/23. The total PageRank for both sites is 92/23 = 4. Hence, adding a link has no effect on the total PageRank of the web. Additionally, the PageRank benefit for one site equals the PageRank loss of the other.

5. The Effect of Outbound Links (continued)

This article reproduced with permission of eFactory.
© 2002 eFactory Internet-Agentur KG Online-Marketing - written by Markus Sobek
PageRank and Google are trademarks of Google Inc., Mountain ViewCA, USA.
PageRank is protected by US Patent 6,285,999.