Imagine what might happen if one were to run a controlled experiment, pooling a group of students and randomly assigning them to different schools. Would the "good" suburban school really do better than the "failing" urban school, once the population of students is similar?
...For the most part, consumers and taxpayers would rather not know whether education, health care, and foreign aid are cost-effective. Instead, people would rather "trust the experts" and attribute high skill levels to educators, doctors, and aid agencies. And, of course, the experts would like us to continue to pay their salaries without questioning their results. As on many other issues, in seeking cost-benefit analysis economists are fighting an uphill battle.
UPDATE: a reader thinks that the preference for ignorance is related to the Seersucker Theory of J. Scott Armstrong.
People are willing to pay heavily for expert advice. Economists are consulted to tell us how the economy will change, stock analysts are paid large salaries to forecast the earnings of various companies, and political experts command large fees to tell our leaders what the future holds. The available evidence, however, implies that this money is poorly spent. But because few people pay attention to this evidence, I have come up with what I call the "seersucker theory": "No matter how much evidence exists that seers do not exist, suckers will pay for the existence of seers."