Mathematics of the Small-World Phenomenon (from Networks, Crowds, and Markets)

Includes a discussion of Stanley Milgram's famous experiment ["with a budget of only $680, he set out to test the speculative idea that people are really connected in the global friendship network by short chains of friends.. he asked a collection of 296 randomly chosen 'starters' to try forwarding a letter to a 'target' person, a stockbroker who lived in a suburb of Boston.." & found that the MEDIAN length of successful paths was just six] and clarifies a common misconception about it:

"It doesn’t establish a statement quite as bold as 'six degrees of separation between us and everyone else on this planet' - the paths were just to a single, fairly affluent target; many letters never got there [all but 64 in fact]; and attempts to recreate the experiment have been problematic due to lack of participation."