To describe something as ‘policy based evidence making’ is to be deliberately rude at two levels, first because it implies the use of evidence to conceal rather than illuminate, but secondly because it implies a failure to recognise that evidence should drive policy (and thus, though often less explicitly, politics).
Evidence based policy, on the other hand, is a thing of virtue for which we should all be striving. That much is obvious to right-thinking people. In recent times, the generality of that thought has been reinforced by very specific approaches. If you haven’t tested your approach through randomised controlled trials, how can you know that your policy making has reached the necessary level of objective rigour?
This post is a thoughtful critique of that position. At one level, the argument is that RCTs tell you less than they might first appear to. At another level, that fact is a symptom of a wider problem, that human life is messy and multivariate and that optimising a current approach may at best get you to a local maximum. That is of course why the social sciences are so much harder than the so-called hard sciences, but that is probably a battle for another day.