Woz - 12:53 am on Aug 11, 2008 (gmt 0)

This question seems to resurface every now and then, possibly because there is no definitive answer.

First, it is important to realise, as you stated, that each of the keyword tools (KeywordDiscovry (KD), Wordtracker (WT) and the Google Keyword Tool (GKT), to name the most prominent three at the moment) takes their data from very different data sources and sample sizes. According to their respective websites, WT pick up their data from the metacrawlers Dogpile and Metacrawler, KD from search engine logs and other sources, thought to be ISP logs. Presumably the GKT data comes from actual Google Searches.

Second, each of the services will "clean" their data using different methods, and will present that data in yet another set of different methods.

Which means it is a mistake in my opinion to rely on any one source of keyword data for your research. I have consistently found that each of the above resources will not only present differing figures for phrases, but will always present phrases that the other two don't. IE., relying on any one source for keyword research results in a very lopsided view of the actual market depending on the idiosyncrasies of the chosen source. You could be missing out on opportunities by not fully researching the market.

You are then left with the challenge of dealing with the discrepancies in figures caused by the differing sample sets. My solution is to homogenize the data by applying factors to the figures based on their estimated sample set size, and then average the figures for each phrase. What those factors are is up to you as your needs may be or are different to mine.

Of course, I am only mentioning three data sources in my example above. There are in fact many, many more data sources if you go searching for them, even more if you are prepared to collect the data yourself. ;-)

Once you get your site up and running then you have the opportunity to fine tune the collected keyword data based on your own logs, analytics and onsite search data.

To look at the problem a different way, Oranges, Lemons and Limes all belong to the the Citrus family, but are of themselves very different fruits. They each make marvelous marmalade when used separately, but when used together make an all-together different marmalade with aspects of them all, but a gestalt that is something unique, and certainly more than the sum of the individual fruits.

Onya
Woz