[nonesuch]

Som time ago I heard of this phenomenon where the average of the estimate of, say, jelly beans in a jar by a group was always closer to the actual number than any single guess of an individual member of the group.
Assuming this is true, what is the name of this phenomenon?, is there some statistical reason this should occur?, and could an apologist for democracy make use of it?

[mikema63]

This tends to be more statistical than anything else, people are, on average, able to estimate things fairly well.

It cannot really be extrapolated past things we all have experience with though, most people can estimate beans, most people do not understand narrow fields of study and large bodies of knowledge.

On average, Americans don't believe in evolution, for example.

[Orestes]

Wisdom of the crowd is what you are thinking of.

I wouldn't put that much stock in it, for the reasons mike mentioned.

[Torus34]

The trick is to make use of the crowd wisdom when applicable to dealing with a problem. Like any tool, it has its uses when wielded by someone knowledgeable in its potential and limitations.