Google PageRank history
The Google PageRank history page displays your domain PageRank information changes through time.

You can access the PageRank history page by clicking on the PageRank information in the domain list or clicking the Information tab in your domain navigation menu.

History
In the History section you find a graphical representation of the domain PR values through time. The stepped chart immediately reveals changes in your PR value so that you can easily understand when the PR increased or decreased.
At the bottom of the chart there's a quick summary of the PR history for the domain containing the maximum and minimum PR value ever recorded, the current PR value and a calculation of the average PR value for the domain based on the number of historical records we have in our database.
Values
The table on the left in the Values section lists all the PR history items currently available for this domain.
The pie chart aggregates the PR history records to display the proportional distribution of each PR value. The larger is the sector, the more relevant is that PR value compared to all the other PR values ever recorded for the domain.