Are there known biases in Alexa's traffic data?

Alexa’s traffic data is based on a global panel which is a sample of all internet users. The panel 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.
  • The data panel may not be a representative sample of the global Internet population.
  • 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.

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