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Are there known biases in Alexa's traffic data?

Alexa’s traffic data is based on a global sample. The sample consists of millions of users all over the world. Known biases include (but are likely not limited to) the following:

  • Rankings for sites with relatively low traffic are rough estimates and are subject to greater volatility. Alexa’s data comes from a sample of millions of users and other sources of traffic data; however, the size of the Web and concentration of most Web users on the most popular sites make it difficult to estimate the ranking of sites with fewer than 1,000 monthly users.
  • Global traffic ranks of 100,000+ should be regarded as rough estimates, as the data used to calculate these ranks is sparse. Conversely, the closer a site gets to #1, the more reliable its data.
  • The higher ranked a site, the more you should expect its rank to ‘bounce around’ due to long-tail effects.

If your site’s metrics are Certified you can display ranks based on Certified Metrics for your site, instead of ranks based on our global sample.

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