KEI (Keyword Effectiveness Index)

KEI(Keyword Effectiveness Index) is the ratio between the popularity and competitiveness for that keyword.

Basically The KEI compares the number of searches with the competition for a keyword to pinpoint which keywords are most effective for your campaign.

It will be cleared by this Example:
Suppose the number of searches for a keyword is 500 per month and Google displays 500,000 results for that keyword. Then the ratio between the popularity and number of search results for that keyword is 500 divided by 500,000. In this case, the KEI 0.001.

If a Keyword have the higher KEI, this means that keyword is more popular and less competitive. That means if you promote this keyword than you might have better chances of getting on Top.