Why Do Keyword Tool Search Estimates Vary so Much?

SEO Question:

I am using Overture, Wordtracker, and KeywordDiscovery to do keyword research, but I want to know why the search volume numbers vary so much, and which numbers I should trust. How do I do keyword research?

SEO Answer:

Each keyword data source has flaws inherent to its model. Rather than looking at keyword suggestion tools as something which offers an exact quantitative measure of traffic look for them to be more qualitative (ie: rather than looking for exact numbers look for them to be more of a yes no tool).

Also look at keyword depth, related words, and reasonable modifiers. Depth and related words matter far more than just the sheer volume for a generic term because the longer queries are more targeted and thus easier to monetize, and longer search phrases are typically easier to rank for than shorter keywords.


Overture is owned by Yahoo!. Since Yahoo! is a major search provider and has a fairly open ad inventory system they have a ton of automated search queries from things like

  • rank checkers

  • search result scrapers
  • people doing competitive research
  • arbitrage players
  • bid checkers

When I searched for "seo book" as a keyword Overture returned 1,579 monthly queries. This number is low because those people searching for my brand (or seo products in general) are typically more likely to search on Google.

When I searched for "seo book" as a keyword Overture returned 33 monthly queries for book engine optimization search seo seo seo software. Notice how they returned the words in alphabetical order, the words in the search queries most likely were in a vastly different order. Also note that is an absurd search phrase. Like who would search for something like seo book seo search engine optimization seo software? Probably nobody, so it is most likely an automated query. You can also back up the lack of legitimacy of that keyword phrase by the fact that Overture did not show any search volume for other similar but shorter and more reasonable queries.

Another problem worth noting with Overture data is that they run singular and plural search words together. Some queries have far different meanings and/or far different search volumes between the singular and plural versions.

Although I mentioned this above, it is worth noting again: keyword depth matters far more than the sheer volume for a generic term. Longer queries are more targeted and thus easier to monetize. Plus those queries are easier to rank for. Since seo book only had 3 returned queries, with one of them being brand related and another being likely a fake query, it probably would not be a great keyword to target for traffic (but the lack of competition and limited market depth might make it an easy term to brand...which was part of the thought process when I created this site).

To test keyword depth and find related keywords you can use a variety of tools, like Overture, Google Suggest, the AdWords Keyword Tool, and Google Sets.

I also have ownership in one of the top ranked Forex websites. Because of the highly commercial nature of the search term (forex means foreign exchange, which is typically searched for by people trading money) Yahoo!'s search estimates (93,240 searches a month) are absurdly overblown for that core term.

But on a positive note, that market has amazing depth. People are looking for courses, books, news, tips, and strategies on the topic. Forex also has synergistic related keywords like currency trading, forex trading, currency exchange, and modifiers galore including types of trades, country names, and currencies. While the market is exceptionally competitive the depth still makes it somewhat appealing.


Wordtracker has a much smaller data set than Overture (Yahoo!), Google, or even MSN, so Wordtracker numbers are going to be more easily skewed by the small sample size. If I use one of Wordtracker's partner search engines and search for an uncommon query it is going to make that query seem far more important than it is.

Digital Point offers a free tool which compares Wordtracker and Overture values side by side.

Keyword Discovery:

I view Keyword Discovery as being somewhat similar to Wordtracker. Keyword Discovery may have a larger keyword index than Wordtracker, but don't expect either of them to offer precise quantitative data.

If you want to test the quantity of traffic for a specific keyword, set up a search targeted campaign on Google AdWords, and ensure you bid enough to show up somewhere on the lower half of the ads on the first page. Also ensure that you target your ads to the appropriate regions, and use a large enough budget that your ad shows up on almost all of the searches for that particular keyword.

In the past I did a more comprehensive review of keyword research tools. I also offer a free keyword research tool which is powered from Overture data and cross references most of the useful keyword research tools on the market.

Published: September 16, 2006 by Aaron Wall in Q & A


September 16, 2006 - 2:07pm

What are your thoughts on Keyword Country? It seems to be the most prices and less known tool out there. I am going to try it because it seems to be the best. But I know I need to have my tools in place to use what I find before I pay the money.

Can you look it over and give us your opinion?


September 16, 2006 - 8:43pm

Google now makes it easy to get ad click estimates (and thus rough approximations of search estimates) and bid prices. Most of that other data is easily and readily available via other online tools.

The only big value add would probably be the number of competing advertisers, but keep in mind that if there are lots of advertisers on search that does not mean there are lots of advertisers on adsense or that they are bidding as much. Google's keyword research tool offers a bar graph which shows the estimated advertiser competition, and Overture also makes it somewhat easy to glance at how much competition there is for a keyword.

September 18, 2006 - 11:55pm

I really detest how much disparity there is between all of the tools...I guess it's because they are all pulling from various data centers and time periods...

When doing KW research , you really have to come to grips with the fact that you are just looking for TRENDS, not hard numbers, and this should help GUIDE your selections, not be the 'be all and end all'. But if you want more assurance on the terms you're selecting, testing out terms on PPC is a good way to guage the relative accuracy of these tools.

I used to use WordTracker but now am growing fond of Keyword Discovery...I find the interface better and the results more in line with what I see in PPC impressions. Plus, it's easier to export and work with the data in my opinion.

Anyway, that's my two cents.

September 19, 2006 - 1:39am

This is good detailed information about various keyword tools out there. After all that's said, which keyword tool do you recommend to use or would you recommend a combination of a bunch?

September 21, 2006 - 3:00am

Hi Sylvia
I prefer to cross reference many of them and not just trust one as the single authoritative source.

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