It is hugely reassuring to suggest that decisions should be evidence-based. It sounds safe, sane, sensible. It seems self-evidently right. What else could they be based on? Guesswork? Hope? Prejudice? As a result the concept of evidence-based policy is on the ascendancy everywhere. Politicians love it, because it sounds so reasonable. Policy makers love it because it implies that decisions can be rational, free of bias, proofed against sectional interest. Scientists love it because it offers the opportunity to feed ‘sound science’ into the ears of policy-makers. So it seems an obvious fact that evidence-based policy is a good thing: yet as Sherlock Holmes comments in The Boscombe Valley Mystery ‘there is nothing more deceptive than an obvious fact’. Some caution may be warranted, for there are deceptive layers hidden by the term that are easily overlooked. Continue reading →