Georgie Porgie, Puddin' and Pie, Didn't like links and made them cry,
When the links came out to play, Georgie Porgie ran away
Two alternatives to Alexa data - Quantcast and Compete
Alexa website data is, as we all know, golden poo for web data statistic hunters.
In the words of Rand Fishkin from SEOmoz: "Alexa data is slightly better than random guessing".
Alexa is part of the giant online retailer Amazon and their web data is collated through their toolbar.
Many years ago when I tried the Alexa toolbar it sent my anti-virus software into a frenzy as it was reporting it as malware, but presumably they have resolved that problem by now.
They rate the entire web with a numeric index with Google.com being at number one as the world's most popular webiste, and this site, Dofollow 001, being at 238,296.
As anybody who has undertaken just a cursory inspection of their rankings will testify that anything out of the top 50,000 is highly inaccurate.
Presumably they sell their data to commercial companies who are keen to analysis on-line user habits.
Although credit where credit is due as Alexa donate their full web index scan to the Internet Archive for all to use.
There are though two alternatives to Alexa if you are seeking out data on a website other than your own.
The first is Quantcast. Quancast is dependent on the webmaster signing up for their service and placing a snippet of Javascript code in their site.
Like Alexa they have a global ranking system with Google.com at number one, and other websites like Sphinn at number 315,885 and Searchengineland at 9,760.
The problem with Quantcast is that it depends on the site owner actually opting in otherwise rough estimates are given or no result is returned at all.
The detail in the data provided for those sites that have opted in is very useful and complex though (see the above examples).
Compete is another, perhaps more thorough, data stats service.
Compete data is collated from over 2m web users who have chosen to opt in and have their browsing habits recorded.
The free version provides information on monthly unique visitors and referral sites. The paid service starting at $199 per month offers more detailed statistics.
The big drawback to Compete is that it is not global but only based on US data.
So what use can Compete play? To give an example I have just recently received an email from a certain SEO blogger who I'm not going to name. I must have commented on his "dofollow" blog. In this email he makes the claim that he has received a phenomenal 17,000 plus unique users in the first three months of the blog's existence.
Checking the Compete data I do indeed see that he is telling the truth but when I look at the referral sites I notice Traffic-Splash and StartXchange listed. There has also been a lot of referrals from Digg, which makes me speculate that if this person isn't above artificially boosting his number of visitors then possibly he has been buying Digg votes too.
So here are a number of sources of website data which could be useful if you are considering placing an advert on a site or some other type of business transaction. Together with other sources they will provide a rounded picture of the user base of any particular website.
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Not enough data
I believe these ranking site still don't have enough data. My own website for example is undetected by compete. while in alexa my ranking is about 300k.
Maybe because what you said above. Compete is not from global data. It is limited from US Data.