Take the number of vehicles in the field, (A), and multiply it by the probable rate of failure, (B), then multiply the result by the average out-of- court settlement, (C). A times B times C equals X...If X is less than the cost of a recall, we don't do one. What applies to the Car Industry (via Dialogue from Fight Club) applies to the Chemical Industry in Spades. DuPont Knew (or strongly suspected) that C8 & (Teflon)…
It's called the "Hand Formula" and you are only liable for negligence when PL > B, where P is the probability of loss, L is the gravity of loss, and B is the cost of avoiding the risk.
In practice though, it can be hard to argue that sort of thing. It's a little academic.