He begins with a historical illustration from a 19th century county fair in England. 800 people entered a contest to guess what the weight of an ox would be when it was butchered. While some of the contestants were familiar with livestock, most were essentially ignorant. When all of the guesses were averaged together, the collective guess was that the ox would weight 1197 lbs. It's actual weight was 1198 lbs. None of the individual guesses were close.
He gives examples from a variety of fields, including the stock market, the gaming industry, google, and politics, and concludes that, given the proper conditions, the collective wisdom can generally be counted on to be better than that of individuals. Those conditions include diversity, independence, and decentralization.
The first year of the Partnership for Missional Church process is spent in learning to listen. Another way of saying that is that we have been learning to practice collective discernment. This book seems to underscore the value in the process, if the group has enough diversity and independence.
A couple of specific passages caught my attention. The first, in an illustration on the ignorance of voters (the context is that despite individual ignorance, democracy works exveptionally well)...
Polls show that Americans think that the United States spends 24% of its annual budget on foreign aid. The reality is that it spends less than 1%. (p. 266)
The second passage that caught my attention explains a little bit why diversity is critical...
If you think about intelligence as a kind of toolbox of skills, the list of skills that are the "best" is relatively small, so that people who have them tend to be alike. This is normally a good thing, but it means that as a whole the group knows less than it otherwise might. Adding a few people who know less, but have different skills, actually improves the performance of the group. (p. 30)