Alexa have recently stated that its toolbar has achieved over 10 million downloads worldwide, but I am unsure as to the duration this claim refers to. I am confident to assume that a very large percentage of toolbars will remain installed are being installed and therefore continue to contribute to the accuracy of the Alexa ranking system. But, this does however highlight the need for webmasters, who wish to gain the best rank possible, to install an Alexa widget on their sites.