tedster - 8:46 pm on Mar 28, 2003 (gmt 0)

 A link from a PR site which is low enough can REDUCE the over pagerank of the site it links to

I believe you have misunderstood the math.

The equation ADDS at least some value for every page that links to the target page. There is no reason to plug in a PageRank of 2 for every page in the calculation, as if every page that links to the target page wuold only be a PR2.

But even if you do that, still each added link will only INCREASE the total PR "vote" for the target page, even if by only a small amount.

You have also misquoted the equation. The damping factor is first subtracted from 1, and then that result is added to the product of the damping factor times the sum of all the individual page calculations:

PR(A) = (1-d) + d(PR(T1)/C(T1) + ... + PR(Tn)/C(Tn))

In a real situation, there will be many pages linking to a given target, and each page will have a different PageRank. It would look more like this:

P(A)= (1-.85) + .85*((2/30) + (4/20) + (3/10) ... + PR(Tn/C(Tn))

You can see that no matter how small the page rank, and no matter how many links on the page, still the value of the entire equation can only increase with each added link. The worst case, a PR0, simply adds nothing. But it surely can't reduce the total value.

[edited by: tedster at 8:48 pm (utc) on Mar. 28, 2003]