If you are to compare the results of different keyword tool search estimates using just one keyword, you will notice that they vary. Moreover, the difference is so significant that it may not be considered just a slight discrepancy between them. What is the reason behind this? Does this mean they are all unreliable?

A number of SEO experts have ventured on these queries and according to their studies every keyword data source has flaws. Said flaws are inherent to its source. These tools offers quantitative measure of traffic however, you have to see them in a qualitative perspective rather than looking at the exact numbers. Also look into the keywords depth, modifiers and related words. Usually, longer search phrases are easier to rank than shorter keywords.

Here are some comparisons between keyword tool estimates:

Overture

Yahoo owns this tool. Since Yahoo is a major search provider, the same is fairly open to almost all types of automated search queries. Further, the depth of keyword is deemed more appealing.

Wordtracker

Compared to Overture, Wordtracker contains limited set of data. Hence, keywords are easily skewed by the limited data.

Keyword Discovery

Keyword Discovery and Wordtracker are somewhat similar. The latter may have larger keyword index nonetheless, both of them may not offer accurate quantitative data.