Alexa vs. Compete Numbers... Any correlation?

[BostonDomainer]

Whenever I am considering a new buy particular when the focus is purchasing based on a traffic asset, I here and there look at the Alexa and Compete numbers. But as of late, I've noticed that they don't really complement each other. For instance Here are the numbers for a name I'm negotiating for

Alexa Trend/Rank:
The lower the rank the better. #8,225,510: Down 3,706 ranks over the last three months.
Compete Rank:
#24,433 with 79,213 U.S. visitors per month

Usually with that number of visitors per month (compete is usually on the low side) the Alexa numbers would be in a mid-high xx,xxx range.

Any thoughts or insight or the algorithms they use or models?

 

[ascii0101]

Two competitors using different algorithms so I would assume different outputs. I use both Alexa & Compete however there is only so much truth shown

Here's some info:
http://www.socialmediaexplorer.com/2009/01/19/determining-website-traffic-tool-review-competecom/
http://www.seomoz.org/blog/competecom-metrics-an-interview-with-jeremy-crane