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Why I think this, is because when you go to the google home page and you click on the google tour home page, you get to this page [google.com...] which has a PR8. This value is a guestimate value as it is not in google's database yet (has no cache).
There are 3 slashes in the URL so for a PR10 page the guestimate PR should be 7 but it's not its 8.
Type these imaginary URL's into the address bar look at the PR and you'll see what I mean.
[dmoz.org...]
[google.com...]
both PR10 home pages but different guestimate PR.
Not sure of the significance of this, but I thought it was interesting all the same.
This fits well with Google's directory PageRank [directory.google.com] being 44 out of 40 as pointed out by Chris_R.
Perhaps googles home page has a value of exactly 11 and all other pages are ranked somewhere between zero and 11. As if all pages have a value relative to googles home page.
No mystery why the guestimate is 8. They aren't Spinal Tap.
The difference with the URL's you gave is that they are not guestimate values of PR.
Go to any page rank 10 page and put in a bogus URL
For example
With 3 slashes the page rank always drops to 7
You can try it with any website you like, it drops a page rank with each directory if it's a guestimate.
Now do it with google and it drops to an 8 so google's home page is PR11
No that's not what it means. Click these:
[google.com...] PR9
[google.com...] PR8
[google.com...] PR7
[google.com...] PR6
So
[google.com...] PR10
[google.com...] PR9
[google.com...] PR8
What's the mystery? (The index.html is ignored as always.)
Both have a PageRank 10 for the Root directory.
So they should have the same PageRank.
For example:
[google.com...] 9
[google.com...] 8
[google.com...] 7
[apple.com...] 8
[apple.com...] 7
[apple.com...] 6
Good heavens why? That's not written anywhere nor consistently true around the web at all. Many guessed pages have a rank the same as the "parent" level above when the parent is a high PRX. Some guessed pages drop two slots. (I just created a DMOZ category page that did just that.) Pagerank is logarithmic, you guys know that.
from a simple functional spec point of view think about:
you put in a url for a genuine site www.foo.com, and you get a measure of its PageRank - for examples sake say 10.
you then change that url to www.foo.com/foo/foo/foo which is a fictitious page. The toolbar is now saying that page has a PR of 7. but we know the page is fictitious. if the page is fictitous it DOESN'T have a PR value.
so doesn't that show that the toolbar is calculating the PR it is displaying based on an examination of the URL - and nothing to do with hooking back up with the google mothership and querying the exact PR for the page you have just entered?
if you think about the kind of load being put on google's servers if everytime someone with a toolbar installed browsed the web it made a call home you'll see why i think the PR in the toolbar is internally-calculated, and no accurate measure of a page's PR.
it is sure the best indicator we've got - but i would want to base my entire googlology on its results
[note to self: is googlology a word?]
I think this is the answer. And, consistent with the directory suggesting that Google has a PR of 11. PR is obviously log scaled. I presume the highest value is 11. The toolbar seems to always round down. Since the highest value the toolbar can show is 10, an 11 shows up as a 10. The toolbar doesn't show a 9 until PR becomes 9.99.
It is all relative. Nothing has changed except the way google is displaying stuff on the toolbar.
By guess is they probably didn't want to hear a bunch of complaining as in reality - google may be the only PR10 site out there.
Everything gets shifted - google has chosen not to shift stuff - but rather add to the top.
I am guessing, although I may be wrong, Google has the highest absolute PR of all sites. *Some* site has to have more PR than all the others. That there is more than one PR10 site out there proves that all PR10s are not equal.
A page with PR10 can actually be 10.something, even 10.999999999999. So, 10 is not the top, the (theoretic) top is 11.
You can understand this if you deeply observe the directory PR bars. They use a multiplicator of 4 just to obtain a wider bar, but if you follow all the values of the scale, you'll reach the top value of 11:
0-4 (5 units)
5-10 (6 unit)
11-15 (5 units)
16-21 (6 units)
22-26 (5 units)
27-31 (5 units. it was 27-32 before, following the 5-6 units path, but Google changed it recently)
32-37 (6 units)
38-43 (6 units) (that is 43.9999etc... Divide it by 4 and you get a theoretical top of 11)
The values used for each step of the scale was probably set manually, but they clearly lead to a top of 11.
Unsurprising, Google homepage shows PR11 (44 pixels) in the directory. Maybe because the PR theory is based on a "googlecentric" model of the web, or more probably because Google really has a PR value of 10.999999999999, rounded to 11.
I wrote an article about this subject and the PR calculation, with a simple picture of the PR distribution. You can find it in the articles section of the website in my profile, but it's in italian! ;)