Return on investment (ROI) is a measure of the successfulness of an SEO campaign. In the strictest sense, it is how much profit is returned from the investment. If money invested in a website promotion campaign produce sufficient profit to cover the campaign costs and still has a positive influence on Earnings Before Income and Taxes (EBIT), then the campaign should be launched. Likewise, if a campaign does not produce a profit, it should be abandoned in favor of other promotional vehicles.

But, it is often difficult to measure the specific profit from a website promotion campaign. That is because, not unlike most promotional efforts, it is difficult to isolate whether a visitor has made a purchase based on a single promotional strategy or the combination of may promotional strategies. For this reason the success of a website promotion campaign is typically evaluated based on the number of visitors it achieves. And since the number of visitors is intimately related to ranking results for high quality keywords, achieved ranking is a fair measure of the success of an SEO campaign.

Since there are many types of website promotional campaigns, your money should be prioritized where it will return the greatest value first. The following table will help define a sensible strategy of prioritizing your promotional budget.

¹ Click-through: number of times a visitor clicks on a link to a website.
²Rank: website rank position for search engine result.
³Visitor %: Number of visitors expressed as a function of keyword popularity.
⁴Market Share: number of search engine searches expressed as a function of keyword popularity.
⁵Cost per visitor: The estimated cost of a promotional campaign divided by the estimated number of visitors.