Interesting question! I was just thinking about this today, before I noticed the thread. My collection is almost a perfect split between small, medium, and large folders (as defined here). I generally lump my 3.75"-4" blades in with the four-inchers, because they tend to feel like large knives to me; having those count as medium in this thread skews my numbers a bit. One thing I've just figured out -- after pulling a bunch of my smaller knives out to evaluate a potential addition to my collection -- is how much of my focus over the past couple of years has been on ~3.25" and ~4" blades. The legal limit in my city is 3.5", so when we first moved here I initially focused on that size; capable, medium, and as large as I can carry. But over time, unconsciously, I've gravitated more towards either side of that length.