What is Keyword Effectiveness Index (KEI)
And can it be useful for your Keyphrase Research.

By Wolfgang Jaegel and Gregory Smyth

The Keyword Effectiveness Index (KEI) compares the count result (number of times a keyword is searched within a search engine) with the number of competing web pages to pinpoint which keywords are most effective for your campaign. In combination with some common sense, this is a great tool to select high conversion key phrases you want to target. Always keep two basic rules in mind.

  • Every tool is only as good as the person using it;
  • Conversion is king!

Don't expect customers or clients to speak your language to find you on the web -- instead use their language. Using the same vocabulary as your customer means that they know you understand their needs and that you can provide them with a solution.

KEI was first introduced by Sumantra Roi. He said that KEI was a measure of the effectiveness of a keyword for your web site. The KEI formula is based on three axioms:

  • the KEI for a keyword should increase if its popularity increases;
  • the KEI for a keyword should decrease if it becomes more competitive. Competitiveness is defined as the number of sites which Google displays when you search for that keyword using exact match search (i.e. you should use quotes around the keyword);
  • if a keyword becomes more popular and more competitive at the same time such that the ratio between its popularity and competitiveness remains the same, its KEI should increase.

Roi's formula behind these assumptions were as follows:

KEI = (Pˆ2/C)*1000
(p=popularity / search count; c=competing sites in Google for that key phrase).

Roi said that KEI is the square of the popularity of a keyword multiplied by 1000 and divided by the number of sites which appear in Google for that keyword.

A common rule on how to interpret KEI results is that keyword or keyword phrases less than 10 are considered poor keywords, while keywords above 10 are good keywords. Keyword or keyword phrases above 100 are excellent keywords and should be displayed on your website's home page.

With time other formulas have emerged, for example

KEI = (Pˆ2/S)*1000
(p=popularity / search count; s= Google matches for "allintitle" for that key phrase).

With more and more "formulas" emerging and many SEO professionals advocating their own 'proven' way to calculate and interpret the optimal KEI (I also have my own methods) it is important to apply common sense and not blindly trust KEIs provided by the different SEO tools. Always ask yourself: "does this make sense for my site and will it convert users into clients?" In the end it is just a ratio, but a very effective one if combined with the most important thing we trust -- our own common sense!