Using Keyword Search Statistics to estimate demand

[Macbeth]

Hi I have used a number of tools, maybe the wrong ones, and the #*$! service.

However, I feel somewhat dissatisfied because the only one I trust is wordtracker as you know how many searches have been performed and in the search engine searched.

What I would really like is a keyword tool that brings up not only the amount of searches last month but for each month in the past 12 months. Does one exist?

Does anybody know of a desktop version of wordtracker that is good and suggests alternative keywords (like a thesaurus)?

Answers please!

[Macbeth]

PS I am using this as method of ranking and deciding which of my ecommerce projects are worth pursing my estimating market demand.

In the past i have winged it with some success now I would like to quantify my decisions.