RANDOMISED controlled trials form the basis of modern medicine for good reason: they are the only trustworthy way we have for evaluating interventions. Their usefulness is not limited to medicine, however. They can be designed to test the effectiveness of many kinds of policy, from education to crime.
Such trials often reveal that policies do not work, or worse. School-based driving lessons, for instance, have increased the number of car accidents (see 鈥淟et science rule: the rational way to run societies鈥�). As the saying goes, the road to hell is paved with good intentions.
So why aren鈥檛 rigorous trials of policies standard practice? One reason is that policy-makers and their supporters don鈥檛 like it when their ideas are shown to fail. Take programmes in the US to promote sexual abstinence among young people. There are two issues here 鈥� is it desirable for teenagers to be abstinent, and do the abstinence programmes work? Many people who answer yes to the first question won鈥檛 accept that the answer to the second is no.
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Science can never tell us what a society鈥檚 aims should be. But once we decide on those aims, science is the best way to find out which policies will help achieve them. There is outrage when patients die because drugs have not been properly tested. We should be equally indignant if people die because of untested policies dished out by politicians.