The 30 percent shrink number on beef tallow finally clicked for me

I was reading through an old copy of The Butcher's Advocate from 1962 that a retired cutter in Omaha gave me, and it said trim loss on a whole primal can run up to 30 percent once you factor in fat caps, silverskin, and bone. I always eyeballed it before and figured I was losing maybe 15 percent, so I actually weighed my next two strip loins before and after trimming and the real number came out right around 27 percent. That gap is basically my whole margin on a busy Saturday, so now I plan my case around the trim number instead of guessing. Has anyone else tracked their actual yield and been surprised by how far off the old guess was?