The quintessential blank slate

11th June, 2005

Dear Economist,
I find that increasingly my decisions are being made based on “rankings” of a sort. I choose recipes from based on the number of forks each recipe has received. I check my books on to see how many stars they received. But I’m worried that these rankings are self-perpetuating. How can I choose better recipes and read better books?

— Tim Bartlett, New York

Dear Mr Bartlett,

Your trust in other people’s taste is touching, and may occasionally be sensible. James Surowiecki’s recent book, The Wisdom of Crowds, has made famous the fact that some problems, such as guessing the weight of an ox, are better solved by averaging the guess of a large number of people than by asking a farmer.

The wisdom of crowds applies only to common-value problems, where the answer is an objective truth. Collective wisdom about a recipe means nothing unless we are all questing after the Platonic form of a recipe for ratatouille; but if so, the more opinions we seek, the closer we will get.

Unfortunately, as you recognise, a recipe may be popular simply because people choose from the ranking tables. A better ranking system would not allow people to see the list of popular items until they had made their own choices, and would discount heavily any choices then made by clicking on the “most popular” charts.

Otherwise, the wisdom of crowds is obscured by “herding” behaviour: when you log into you decide that whatever your prior beliefs about the virtue of Harry Potter might be, 18 billion fans can’t be wrong. Because you rely on the opinions of others, your choice reveals no new information and the rest of us do not get to benefit from whatever insight you might have had. Since you are evidently the quintessential blank slate, this may be no great loss.

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