Useful for thoughts about evidence based policy making:
Let me re-iterate my bottom line. Yes, experiments can be costly. Yes, sometimes they are simply impractical. And yes, occasionally they are unfair. But the truth is that the policy world is full of experiments. The experiments have all of these disadvantages. But because they’re conducted in a sloppy way, without proper randomisation, protocols, independent evaluation or serious attempts to identify a comparison group, they are experiments from which we learn very little. The choice isn’t between experiments and no experiments. It’s between useless experiments and useful ones.