Maybe that's a poor way of stating the problem. In a zero tradeoff world, 0 deaths would be optimal. We don't live in that world though. For example, flying is

Maybe that's a poor way of stating the problem. In a zero tradeoff world, 0 deaths would be optimal. We don't live in that world though. For example, flying is supposedly safer than driving. Airplane crashes happen. We could demand zero deaths from the planes which would drive the costs up, causing more people to choose to drive, causing more deaths. So, in relation to airplanes, we can't choose zero deaths in the real world. We have to choose some imperfect trade off, otherwise we'll cause more deaths.