Jury Theorems

Jury theorems are mathematical theorems about the ability ofcollectives to make correct decisions. Several jury theorems carry theoptimistic message that, in suitable circumstances, “crowds arewise”: many individuals together (using, for instance, majorityvoting) tend to make good decisions, outperforming fewer or just oneindividual. Jury theorems form the technical core of epistemicarguments for democracy, and provide probabilistic tools for reasoningabout the epistemic quality of collective decisions. The popularity ofjury theorems spans across various disciplines such as economics,political science, philosophy, and computer science., This entry reviews and critically assesses a variety of jury theorems.It first discusses Condorcet’s initial jury theorem, and thenprogressively introduces jury theorems with more appropriate premisesand conclusions. It explains the philosophical foundations, andrelates jury theorems to diversity, deliberation, shared evidence,shared perspectives, and other phenomena. It finally connects jurytheorems to their historical background and to democratic theory,social epistemology, and social choice theory.