Toolbar Pagerank
First, let me explain in more detail why the values shown
in the Google toolbar are not the actual PageRank figures.
According to the equation, and to the creators of Google,
the billions of pages on the web average out to a PageRank
of 1.0 per page. So the total PageRank on the web is equal
to the number of pages on the web * 1, which equals a lot
of PageRank spread around the web.
The Google toolbar range is from 1 to 10. (They sometimes
show 0, but that figure is isn't believed to be a PageRank
calculation result). What Google does is divide the full range
of actual PageRanks on the web into 10 parts - each part is
represented by a value as shown in the toolbar. So the toolbar
values only show what part of the overall range a page's PageRank
is in, and not the actual PageRank itself.
Whether or not the overall range is divided into 10 equal
parts is a matter for debate - Google aren't saying. But because
it is much harder to move up a toolbar point at the higher
end than it is at the lower end, many people (including me)
believe that the divisions are based on a logarithmic scale,
or something very similar, rather than the equal divisions
of a linear scale.
Let's assume that it is a logarithmic, base 10 scale, and
that it takes 10 properly linked new pages to move a site's
important page up 1 toolbar point. It will take 100 new pages
to move it up another point, 1000 new pages to move it up
one more, 10,000 to the next, and so on. That's why moving
up at the lower end is much easier that at the higher end.
In reality, the base is unlikely to be 10. Some people think
it is around the 5 or 6 mark, and maybe even less. Even so,
it still gets progressively harder to move up a toolbar point
at the higher end of the scale.
Note that as the number of pages on the web increases, so
does the total PageRank on the web, and as the total PageRank
increases, the positions of the divisions in the overall scale
must change. As a result, some pages drop a toolbar point
for no 'apparent' reason. If the page's actual PageRank was
only just above a division in the scale, the addition of new
pages to the web would cause the division to move up slightly
and the page would end up just below the division. Google's
index is always increasing and they re-evaluate each of the
pages on more or less a monthly basis. It's known as the "Google
dance". When the dance is over, some pages will have
dropped a toolbar point. A number of new pages might be all
that is needed to get the point back after the next dance.
The toolbar value is a good indicator of a page's PageRank
but it only indicates that a page is in a certain range of
the overall scale. One PR5 page could be just above the PR5
division and another PR5 page could be just below the PR6
division - almost a whole division (toolbar point) between
them.
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