You don't have to know a lot about animal husbandry to learn the moral of this story: empirical data beats mathematical modeling. But in many ways your business is controlled by people who worship at the altar of Pi. Cars are designed on computers. But an old-time car designer once pointed out we're not building the cars in a digital world, we're building them in a mechanical one. The financial system is built the same way and we've seen how that worked out.

Beware quants bearing models.