To understand the reason for this it’s necessary to understand how the tools that are used for keyword research get their data. Major search engines like Google and MSN do not make data publicly available on the exact number of searches done on their search engines for keywords and phrases. The only major search engine to make search data available is Overture, which is now owned by Yahoo and strictly speaking is not a search engine but a PPC engine. Overture is still one of the major tools used by keyword researchers to determine the number of searches done on different keywords. However for the people who don’t understand how Overture provides it’s data, the results are frequently an over estimate of what happens in reality.
I have personally done research on the degree of these over estimates. I can tell you that for a two word phrase, Overture over estimates the number of searches typical by a factor of 10 to 1. In other words it reports 10 times more searches than there actually are done by real human searchers. My research has also been confirmed by Robin Nobles in her report "Demystifying The Radically Different Keyword Results Provided By Overture and Wordtracker." Robin does SEO Research and writes frequently on her findings. The over estimate occurs for a number of reasons which are too involved to go into here. But the most significant reason is that Overtures results include all those searches done by automated queries from people using tools to do keyword research and search engine keyword ranking checks. So you might ask, why then if the results can be wildly inaccurate should we bother to do the research. Well even inaccurate research is better than no research at all !
Another major tool used for keyword research is available from Wordtracker which unlike Overture is not a free service. However they also provide a limited tool at Wordtracker Free Keywords Wordtracker gathers its keyword data from some of the smaller search engines and then attempts to apply it as being representative of searches on other search engines. This makes Wordtracker results also inaccurate, but for different reasons than for Overture. If you’re feeling a bit confused by now don’t worry everyone uses these tools and until something better comes along this is all there is. Just don’t get too excited by the large number of searches you may see for some keywords or phrases, they’re frequently well over reported. There are many keyword research tools that exist either as free to use online tools or free and paid for software tools. Many of the online tools access the Overture keyword suggestion tool, but one online tool that’s very useful for showing you side by side the differences in the number of searches reported by Overture and Wordtracker is at http://www.digitalpoint.com/tools/suggestion/ I said earlier that Wordtracker is a paid service and it is, but they do offer a limited search for free and that’s what this tool makes use of.
To illustrate what I said about the differences in reported search results try going to the digital point keyword suggestion tool and type in "web hosting provider" without the quotes. I did it using the US database. Now compare the search results shown for this phrase in Wordtracker and Overture. When I tried this the results were Wordtracker 628 searches per day, Overture 26,035 searches per day. In the same list of results look and find "web hosting service provider" compare them again. When I did this Wordtracker showed 207 searches per day and Overture 120 per day. Or what about "web hosting solution provider" Wordtracker reported 191 searches per day and Overture only 15 per day. The problem of course with many of these tools is that apart from showing you at times wildly different results, many of them don’t tell you how many other web pages are using the same keywords. That’s very important to know because this is the competition you face in getting ranked with a search engine. For another Keyword Discovery Tool I use click here Continued at Keyword Research Tools - Part II | 
