If each voter is more likely right than wrong and votes independently, majority accuracy rises with group size.
Condorcet proved it in 1785. It requires competence above chance and independence, and the independence assumption is what fails in practice — correlated errors destroy the result entirely.
In practice
- A jury of twelve is more accurate than any one juror, provided they deliberate on the evidence and not on each other.
- A prediction market beats individual forecasters until everyone starts trading on the same widely shared model, at which point the accuracy collapses.
- Further reading
- Wikipedia
- Subject
- Networks & Collective Behavior
- Essay
- How connections shape what crowds do