Math can say exactly how two people should split the gains from cooperating

If two parties can create more value together than apart but disagree on the split, John Nash showed there's a unique solution satisfying a short list of fairness axioms: each side's share depends on what they could get by walking away, and the final split maximizes the product of each party's gain over that fallback. It turned 'split it fairly' into something you could actually calculate.

— John Forbes Nash Jr., The Bargaining Problem — Econometrica, 1950