Over the past two years, an innovative marketing concept has continued to meander its way through the SEM community. It's known as the long tail of search. "Wired" editor Chris Anderson deftly puts forward the argument that low-demand products can collectively make up a market share that equals or exceeds high-demand products -- if the distribution channel is large enough.

The term "long tail" is a particularly descriptive approach for providing a visual representation of a Zipf or Pareto distribution graph, more commonly known as the 80/20 rule. In these graphical distributions, high-demand products and services rise upward to the left and low demand products and services gradually "tail off" to the right.

A similar statistical distribution occurs when you study search referral traffic patterns. Common keywords compose the bulk of branded search referrals to form the search head, while unbranded and obscure keywords stretch out to make up the search tail. This phenomenon holds true for both paid and natural search.

In many cases, the infrequent search queries - the long tail of search represented above by the graph's extended width - can cumulatively outnumber the more frequent search queries that compose the graph's height. In aggregate form, the long tail keyword phrases compose the majority of search-referred traffic, as opposed to the minority of search terms that fuel the search head.

The long tail principle functions in a way contrary to how most online brands prioritize their SEM strategies. Most online merchants tend to target the search head first, optimizing their sites for the top 20 keywords and keyword phrases that drive the most traffic.

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