Alexa ranking algorithm changed

Last week Alexa changed their ranking algorithm causing the ranking of many sites to be shifted. Currently only 9 months of data is available for all charts using the new ranking algorithm, however Alexa's announcement claims that will change soon.

Since 1998 Alexa was ranking sites based on data gathered by their toolbar. A decade later, Alexa has decided to aggregate data from multiple sources, not just their toolbar. Unfortunately the company is silent on who exactly the additional sources are.