The wisdom of crowds is the finding that aggregating many independent, diverse judgments often produces an estimate more accurate than most individual experts could manage alone.
The idea
James Surowiecki popularized the idea in The Wisdom of Crowds, building on earlier observations such as Francis Galton’s 1907 finding that the median guess of a crowd at a county fair accurately estimated an ox’s weight, beating most individual guesses including experts’. The effect depends on specific conditions: contributors need diversity of opinion, independence from one another, decentralized local knowledge, and a mechanism to aggregate individual judgments into a collective one. Errors that are individually random tend to cancel out in aggregate, leaving the shared signal.
When to use it
- Estimating an uncertain quantity where many people have partial, independent information
- Forecasting or prediction markets, where aggregating many bets outperforms any single forecaster
- Deciding whether to trust a poll, review score, or crowd estimate as evidence
How to apply it
- Collect judgments from a genuinely diverse and independent set of people.
- Make sure individuals form their estimate before seeing others’ answers, to preserve independence.
- Aggregate with a simple, transparent method (e.g. mean or median) rather than letting a subgroup dominate.
Watch out for
The effect collapses once independence breaks down — if people can see and copy each other’s answers, the crowd stops averaging out errors and instead converges on a shared bias, which is the mechanism behind social proof and herd behavior. A crowd that is not actually diverse (e.g. everyone with the same blind spot) will be reliably wrong together.
Related models
- Crowdsourcing — a practical application of aggregating crowd input to generate or filter ideas.
- Social Proof — describes the opposite failure mode, where independence breaks down and the crowd converges on a shared error.
- Small World Phenomenon — describes the network structure through which crowd opinions can spread and lose independence.
Sources
James Surowiecki, The Wisdom of Crowds (2004); Francis Galton, “Vox Populi” (Nature, 1907).