Both the government and the public should be far more sceptical about policies which are purported to be ‘evidence-based’, argues new research released today by the Institute of Economic Affairs.

In Quack Policy – Abusing Science in the Cause of Paternalism, Jamie Whyte exposes how politicians promote regulations and taxes under the justification of scientific evidence, yet the experts promoting these policies often make basic errors and have little or no grasp of economics.

http://www.iea.org.uk/in-the-media/press-release/%E2%80%98evidence-based%E2%80%99-policies-are-damaging-uk-policymaking

Those in favour of evidenced based policies have tended to be dismissive, arguing that this is just a case of lack of evidence, rather than a problem with evidence-based policies per se.

https://twitter.com/bengoldacre/status/370159847985381376

I'm not fully convinced though.  I've started reading Taking the medicine: a short history of medicine's beautiful idea and our difficulty swallowing it by Druin Burch, and this has plenty of examples of people saying something like "Of course, up till now medicine has been totally wrong, but I've got a new way of doing it right" - and then going on to make the same old mistakes. Maybe evidence based practice is the same, just a way of convincing ourselves that we've got it right this time.

As I see it, the trouble with evidence based practice is that what counts as evidence based today doesn't meet tomorrows higher standards.  This means

1. How can we trust evidence based practice if it might be overturned tomorrow?
2. As less gets to count as evidence, evidence based practice gets harder and harder to do.

At the root of this is the insistence that evidence must meet some 'gold standard'.  This seems to be too much the frequentist viewpoint, but in the end we have to be Bayesians, taking all evidence into account.