Alexa is incredibly unreliable

Analysis,Business by on July 28, 2006 at 1:07 pm

I know that the unreliabilities of Alexa are fairly well documented, but my sense is that many people still place too much faith in the numbers that come out of Alexa. This has become incredibly clear over the last few months at Judysbook. We have millions of page views a month, so we should have a reasonable enough sample size for Alexa to at least pick up major changes in our user base.

We’ve had two step-function changes:

  • Step function 1 (4/19): Doubled our unique user count, but overall traffic was level. We saw this traffic jump at the end of a writing promotion (high PVs/visit).
  • Step function 2 (6/26): Doubled our unique user count, and doubled our traffic.

Now, take a look at our alexa charts:

Daily Reach: Should be reflective of unique users
Alexa Dail Reach

Page Views

Alexa Page Views

Our step function changes were lasting changes. Today, our unique user count is 4x what it was on 4/18, and our traffic is 2x. Neither of these changes are at all reflected in the Alexa charts. That is pretty awful. And to think that I used to use Alexa to determine which competitors were larger.

1 Comment

  1. […] There are numerous posts online about how the various online measurement firms present very different views on things like unique users and page views. A few of the better ones I’ve read include Fred Wilson’s ‘Whose Numbers are right?’, Donna Bogatin’s ‘Data Attraction: Hard science or numbers game?’ and Avinash Kaushik’s detailed analysis of how Hitwise and Comscore get their data. I’ve even commented on Alexa’s fallibility w.r.t. Judy’s Book Traffic. […]

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