Tim Harford writes,

What is missing is the political demand for tests of what really works. Too many policies on education, welfare and criminal justice are just so much homeopathy: cute-sounding stories about what works leaning more on faith than on evidence. Politicians and civil servants, faced with some fancy new idea, should get into the habit of asking for a proper randomised trial. And we, as citizens, should be equally demanding.

In fact, the political system is very ill-suited to trial and error learning. That is what markets are for. That is why I favor competitive government.

Thanks to Mark Thoma for the pointer.