Don't me wrong, I want and chase CLIs on the cards that I actually use. The card in question here is one that sits dormant in my SD. It already has a relatively low limit of $4k. Bringing it down to say $500 won't impact my overall utilization at all.
The test of thresholds that I'm looking to perform would involve me reporting a balance on the card of 10%, 30%, 50%, 70%, 80%, 90% and 100%. This would be with all of my other cards reporting a balance of 1%. That's what I currently do anyway; all of my cards report 1% utilization. With my profile, my FICO scores don't change and 1 of my cards reports a 1% balance or all of them report a 1% balance. The second variable that I'd like to test is with all of my cards reporting a 1% balance with one card reporting the percentages I listed above. I'm most interested in the 100% and 50% points, but would like to test the others as well to see at what points I see a score drop and how many points.
It's fairly simple to isolate my test to being the only variable. All I would need to do is pull my 3B scores just prior to the balance reporting, then pull them again after. Scores don't naturally fluctuate much; my 3B scores have not budged a single point in 6-7 weeks now. When they do from something like an inquiry aging, accounts aging, etc. the chances of that happening during the 2 day window or so when I perform a utilization test is extremely small compared to it happening at some other point during the other ~28 days in the month. And, if there's any doubt, I would just test the same data point (utilization value) again.
You are correct that utilization accounts for 30% of FICO scoring and that there is 70% "other" categories. 35% of that however goes to payment history, which with no missed payments (a 100% certainty here) during my testing would eliminate that from the equation. Therefore, there's really only 35% "other" categories, and unlike utilization which is very volatile and only matters for that exact snapshot in time (having no memory) the remaining 35% of what goes into ones FICO scores doesn't change quickly at all.
AU accounts BTW aren't counted into utilization. At least not all of them. I have one AU card on my report and months back I tested whether it was counted into my utilization by allowing all of my other cards to report a $0 balance while the AU card had a balance and my scores all dropped 14-22 points. This proved that the AU card was not being counted into my aggregate utilization.
I'm still not positive that I'm going to try this "test" at all... it was just something I was thinking about since I've got a SD card sitting there with an already relatively low limit that's doing me no good. I'm not in any rush or anything even if I were to do some testing, so this is certainly a topic that I can let marinate for a while before making any decisions.
