How reliable is Alexa in measuring your site’s traffic rank?

Alexa Traffic RankingEven to someone like me who enjoys browsing over site statistics and testing the accuracy of the resulting metrics, understanding an Alexa traffic rank is not an easy task.

Except for the fact that the Alexa traffic ranking system is based on information generated from Alexa toolbar users and that “A site’s ranking is based on a combined measure of Reach and Page Views” plus some kind of “data normalization” which also are not explained, there is not much information about the Alexa ranking system.

In its FAQ, Alexa also stated: “Alexa’s traffic rankings are based on the past three months of global traffic according to our diverse data sources, and are updated weekly.”

Given this minimum traffic tracking period, I wonder how a blog like mine ~ although barely two weeks old ~ was able to attract a traffic ranking. Is it because my blog is hosted by WordPress.com, and Alexa is biased to WordPress.com-hosted sites? I don’t think so. I know of other sites hosted by WordPress.com which have been online for many months now, yet they are still showing an Alexa “No Data” status. I am certain that some people are visiting those sites. (Note: The small Alexa image on this page shows “No Data” for Alexa which we could only surmise that Alexa did not like to make its traffic ranking public.)

I think I will stick to metrics like unique visits, page views and the like in gauging site traffic performances. At least, these figures are easy to understand, and I can explain the figures to other people.

But I cannot say the same thing with Alexa’s traffic ranking. After all, according to Alexa, if a site traffic ranking is beyond 100,000, the figures are statistically meaningless. For a site traffic rank to be statistically meaningful and reliable, a site should be close to the top rank. Quite a tall order, isn’t it?

Alexa’s statements read as follows:

Sites with relatively low measured traffic will not be accurately ranked by Alexa. Our data comes from many various sources, including our Alexa users; however, we do not receive enough data from these sources to make rankings beyond 100,000 statistically meaningful. (However, on the flip side of that, the closer a site gets to #1, the more reliable its rank.)

With many websites that are not even close to the top 1,000 or even 50,000 (let alone #1), I wonder why advertising placement agencies even bother to look at a website’s Alexa traffic rank!