Alexa, if you are not familiar with it, is a service of Amazon.com, international seller of books and products online. One of the services that Alexa provides is “Alexa Site Information,” which includes three main areas:
# Site Overview
# Traffic Detail
# Related Links
There is one slight problem with the way that they gather this data, oh, and they don’t explain it very well either. To be accounted for visiting a website, you would have to have the Alexa cookie or have downloaded the Alexa toolbar.
Understanding how this affects the ranking of a website, Peter Norvig used some data from his website and a few others to explain the problem with this type of data gathering:
Consider the problem of comparing traffic to internet sites. Most sites keep their traffic numbers secret, so you need to rely on third parties that monitor a sampling of traffic. One such third party is the alexa.com traffic rankings. If you download a toolbar from Alexa, your visits are tracked anonymously, and the aggregate statistics are available for all to see. As Alexa explains there are some biases inherent in this process: sites associated with Alexa, such as Amazon.com are overrepresented; sites that use https protocol are underrepresented, and so on. But one bias they don’t really comment is the selection bias: the data would be good if it truly represented a random sample of internet users, but in fact it only represents those who have installed the Alexa toolbar, and that sample is not random. The samplees must be sophisticated enough to know how to install the toolbar, and they must have some reason to want it. It turns out that the toolbar tells you things about web sites, so it is useful to people in the SEO industry, so it overrperesents those people.
Does this mean that Alexa traffic details is not valuable?
Absolutely NOT!
Alexa data and website statistics, like SEO advice, should be viewed as a guide and should be compared with other websites in the vertical that the website is in. Social websites can be compared as can search engines. What would this say about a given website? It gives you the insight to what a website in a given vertical is doing to reach the given group of users. Is this valuable? Of course this is valuable to marketers and should be considered, but not something to live by.
What are your thoughts?
Do you value Alexa rankings?
Do you even consider Alexa?