Calculations and usefulness of Kei

In laymen's terms, the KEI of a keyword or search term is the equation that you end up with that will tell you how easy a particular keyword is to rank for. It is supposed to highlight quite easily which search terms to target in order to drive traffic to your site.
Different variations are there which shows how to calculate KEI effectively, but I use and suggest the following:

KEI = (volume of searches per month)^2/(total number of competitors)

I said at the beginning of this article I would make this as simple as possible, so I will now attempt to explain how the above calculation works in terms of a real example

Cheap bathroom Suites (9900)^2/17700000 = 5.54

So, the KEI of the search term Cheap Bathroom Suites is 5.54. From experience, to find an ideal search term to target that will get results quickly, I would be looking for a KEI of between 20 and 150, so this search may not be the best to target initially!

Sorry to get a little complicated now, but there are reports out there which say KEI is calculated using exact matching search technology. For example, if we search Google by simply typing in our search term (broad match) we get 17,700,000 competing sites, making our search term not ideal to target initially. If we use exact matching searching we get 50,400 competing sites. Let's run our equation again:

Cheap bathroom Suites (9900)^2/50400 = 1944

What a different result we get! Generally the consensus is the higher the KEI, the easier the keyword will be to target, and at 1944 we should be able to hit that in day one.

So what do we believe then? Do we listen to the articles that say that KEI is calculated using exact match search, or by broad match as in my first example? I tend to lean towards the first theory, as if nothing else, the first option will give you the worst case scenario allowing you to make a much more realistic decision.