How accurate is the Google toolbar?

The Google toolbar is not very accurate in showing you the actual PageRank of a site, but it?s the only thing right now that can give you any idea. As long as you know the toolbar?s limitations, then at least you know what you are viewing.

There are two limitations to the Google toolbar:
1. The toolbar sometimes guesses. If you enter a page, which is not in its index, but where there is a page that is very close to it in Google?s index, then it will provide a guesstimate of the PageRank. This guesstimate is worthless for our purposes because it isn?t featured in any of the PageRank calculations. The only way to tell if the toolbar is a guesstimate is to type the URL into the Google search box and see if the page shows up in the SERPS. If it doesn?t, then the toolbar is
guessing!

2. The toolbar is just a representation of actual PageRank. Whilst PageRank is linear, Google has chosen to use a non-linear graph to portray it. So on the toolbar, to move from a PageRank of 2 to a PageRank of 3 takes less of an increase than to move from a PageRank of 3 to a PageRank of 4. A comparison table best illustrates this phenomenon. The actual figures are kept secret so we?ll just use any figures for demonstration purposes:

The PageRank shown in the Google directory (http://directory.google.com) suffers from the same problems. The PageRank shown in the directory is also on a different scale. There have been attempts to cross-reference these two scales but because they are non-linear, the results really do not tell you anything more than you already know.

Also of note is that a programmer managed to generate a tool to look up PageRank without using Internet Explorer. This tool has since been withdrawn, but whilst originally the numbers given by this software and Google?s toolbar matched - presently querying with such software sometimes produces different numbers than querying with the toolbar. This is Google?s right to protect their data, but is the strongest indication that: