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In return, Megan McArdle showered him with contempt. Her post began with a spectacularly telling dismissal. The interview, she snarked, was part and parcel of "Ezra Klein's obsession with experts." I should go talk to some drug industry executives, she advised.

It's the experience of talking to ideologues on both sides of this issue -- some of them industry employees, others activists -- that has actually led me to rely so heavily on, well, actual experts. But McArdle's rebuttal isn't premised on interviews with a different class of experts. Rather, she's relying on a mixture of basic economic theory and intuition. The product, as you might imagine, isn't terribly responsive to Avorn's arguments. "I am completely unsurprised to find out that Dr. Jerry Avorn has completed no work in economics," she writes in her concluding paragraph, "and indeed, so far as I can tell, no work in anything except being a professor of medicine."

So does Tabarrok -- or McArdle -- know as much as Avorn does about the pharmaceutical industry? Of course not. Neither of them is a health economist. Neither of them, to my knowledge, has worked at a pharmaceutical company. Neither of them has had sustained contact with the drug industry. Nor is medical innovation a subject that's dominated by economists. It's something that requires some knowledge of, you know, medicine, and the interactions between public and private research divisions, and the FDA process, and all the rest of it. Economics is a useful discipline. But it's not a decoder ring. And it's not a substitute for discipline-specific knowledge. That's why Tabarrok read Avorn's book, which he called "excellent."

McArdle elides this by spending a lot of time explaining how companies work to Dr. Avorn. Almost all of her post relies on spinning Avorn's comments as if they were about pharmaceutical companies, rather than about whether high reimbursement rates for pharmaceuticals is the most cost-effective spur to further innovation. It's quite a performance.

From the start, the more confident advisers found more buyers for their advice, and this caused the advisers to give answers that were more and more precise as the game progressed. This escalation in precision disappeared when guessers simply had to choose whether or not to buy the advice of a single adviser. In the later rounds, guessers tended to avoid advisers who had been wrong previously, but this effect was more than outweighed by the bias towards confidence.

The findings add weight to the idea that if offering expert opinion is your stock-in-trade, it pays to appear confident. Describing his work at an Association for Psychological Science meeting in San Francisco last month, Moore said that following the advice of the most confident person often makes sense, as there is evidence that precision and expertise do tend to go hand in hand. For example, people give a narrower range of answers when asked about subjects with which they are more familiar (Organizational Behavior and Human Decision Processes, vol 107, p 179).