I know you love to tell everyone to dyor so I'll share some. A...

I know you love to tell everyone to dyor so I'll share some. A basic Google search of "how does Alexa work?" Gives this result:

"The traffic rank is based on three months of aggregated historical traffic data from millions of Alexa Toolbar users and is a combined measure of page views and users (reach). As a first step, Alexa computes the reach and number of page views for all sites on the Web on a daily basis."