Which web traffic ratings system do you trust – your own or the other guy’s?

Recently, a client asked me how to differentiate between the data they collect on their own web sites and the data on free services like Alexa or Compete.com. Here is my response:

When you directly install a system such as WebTrends on your site or use the reporting tool that is built-into the Broadcast Interactive/Clickability system, these systems are directly measuring traffic on your sites by installing tags on your pages that send calls directly to their tracking servers. So, these types of systems tend to be very accurate and (along with comScore rankings which also require tags to be installed on your sites) are generally trusted in the market. Same with Google Analytics.

However, even these systems will vary in their results by 10-15% typically, based on what they define as a ‘full page load’ versus a ‘partial page load’, etc…., given that often times a user will click and navigate away from a page before it fully loads. They will also quite literally vary based where the tags are placed on the site (top or bottom of the page). So, a certain amount of variation is normal and healthy.

Services like Compete.com and Alexa.com are free services that don’t have the benefit of directly installing tags on your sites – instead they use a number of indirect methods of measuring traffic and user engagement. This might include tracking ISP records, dropping cookies on user-machines that have downloaded their toolbar (such as Alexa does) to track user behavior, etc…. kind of like a free version of Nielsen for the web.

In general, then, I’d say you should trust and rely on your direct measurement reports (ie, WebTrends or Broadcast Interactive/Clickability reports), but that you can use Compete or the Alexa toolbar to track relative performance of other sites in your markets.

If you catch a competitor stating that their site gets more traffic than yours based solely on Compete.com records, you should ask that they back it up by releasing their WebTrends, comScore, or Google Analytics reports. This is especially true if you feel that Compete.com is under-ranking your site relative to the numbers you see in WebTrends.

To summarize: trust your installed and fee-based ratings numbers over the free ratings services but use the free services for quick comparisons.