We have a decent amount of idle inventory, way less than the average though. Technically for a dealer parts department, any part with 12 months of no movement is considered idle inventory. We have our system setup to start counting it at 9 months. At that point we start showing them at cost minus on the dealer parts locator. Idle inventory is very bad as not only is it the owner's money being wasted, but it takes the spot of something that actually sells. Also if your idle inventory exceeds a certain percentage, you are disqualified from certain programs from the manufacturer.
So when people ask why we don't have some random part in stock, I tell them "if we sell it enough times we will stock it, but if we haven't sold it in 4 years I am not giving it shelf space." Plus with so many parts that we can get either same day, overnight, or at the worst 2-3 days out it makes no sense to stock some of them.