Most members of a large population are linked by short chains of acquaintance, popularly six steps.
Of 296 initiated chains in the full 1969 study, 64 reached the target, and among those completed chains the mean was 5.2 intermediaries, about six links. The high attrition means this is not a direct estimate that every arbitrary pair of people is six steps apart.
In practice
- Milgram's completed chains averaged about six steps, and only a quarter of the letters arrived.
- A supplier introduction sought through three intermediaries usually arrives, which is why professional networks function without anyone mapping them.
- Possible explanations
- The explanation is that a few long-range ties collapse the distance across an otherwise clustered network, so short chains exist even when almost all ties are local.
- In its favour
- The structural result is solid, has been reproduced in large digital networks where whole graphs can be measured, and the original experiment was an ingenious attempt at a hard measurement.
- Against it
- Only about a fifth of the 1969 chains completed, and completion was correlated with the target's accessibility, so the mean of the completed chains is not an estimate for arbitrary pairs and the famous six is not what the study showed.
- Standing
- About 22% of chains completed, so the mean of the completed chains is not an estimate for arbitrary pairs.
- Subject
- Networks & Collective Behavior
- Essay
- How connections shape what crowds do