Hooves and Priors
By David Henderson
In “Yes Indeed: I Have My Priors About the Minimum Wage,” Don Boudreaux at Cafe Hayek writes:
So an economist whose priors tell him or her that raising the hourly cost of employing low-skilled labor will cause employers to choose to employ fewer hours of low-skilled labor is falling into no unscientific or dogmatic trap. Such an economist is behaving no less scientifically than does, say, a biologist whose priors tell him or her that a zebra’s stripes or a trout’s dorsal fin were formed over time by natural selection. A renegade biologist who insists, say, that a trout’s dorsal fins are unique among all animal features in having been formed by some process distinct from – and, indeed, at odds with – natural selection would have a huge burden of proof to overcome. Not only that, no one would expect other biologists to immediately, simply upon hearing one or a handful of biologists claim unique origins for a trout’s dorsal fin, to start regarding natural selection as a process that works only sometimes. All good biologists, in fact – even those who do not specialize in studying fish – would correctly insist that science, far from requiring that they withhold judgment about whether or not natural selection formed the trout’s dorsal fin, requires that they, given the current state of knowledge in biology, regard natural selection as applying to a trout’s dorsal fin no less than it applies to other biological phenomena.
He says it well. I endorse his thinking, at least the part about economics. I don’t know enough about natural selection to say that part is completely sound. I’m quite confident about the law of demand.
But I’m not writing to take issue with natural selection. I’m writing to make an analogy between what we’re pretty sure of from economics and what doctors are pretty sure of. About 25 years ago, I had some symptoms that made me think I might be having a heart attack. I called my doctor on the weekend and his exchange connected me with one of his partners. The partner asked about my symptoms and what I had been doing just before having chest pains, and he concluded that the odds were high that it was just gas. He told me to eat some bread and see if the problem “passed,” adding that the double meaning was unintended. It did. Later, when I went to see his partner, my regular doctor, to discuss something else, I mentioned that incident. He smiled and said that one of the most important lessons he learned from one of his teachers in medical school was:
When you hear hooves, think horses, not zebras.