## The Initial (or Seed) values

The strangest part of the formula is the little "d".

PR(A) = (1-

d) +d(PR(T1)/C(T1) + ... + PR(Tn)/C(Tn)) .

What good does it do to multiply every page's PageRank by the same factor - and what's the purpose of adding (1-d) to every PageRank?

Consider the simple set-up to the left: Page1 links to all pages - and all subpages link back. This is specified on the spreadsheet like below:

How to specify the simple structure |

**total**PageRank for the 5 pages is 5 - so the average PageRank is 1.

Initial value set to 10 |

Initial value set to minus 1 |

**initial**PageRank of 1 for each page. Suppose we try some other "seed" values - like 10 (to the left) or even minus one (to the right). The results can be seen here and here - and notice that in both cases the average PageRank is getting closer and closer to 1.

Try the spreadsheet for different set-ups and if you have
enough iterations,
the average always become exactly 1 - **as long as you don't have any dead ends**.

So that's the purpose of adding **(1-d)** to every PageRank and multiplying by a dampening factor **d**:
to ensure that the average PageRank becomes 1, or as they say at Stanford,
"Note that the PageRanks form a probability distribution over web pages,
so the sum of all web pages' PageRanks will be one".

Now, let's look at the value of the damping factor.