> The problem with rejecting economics' claim to be a science on the basis its underlying assumptions survive even as models based on them are usually out by a few percentage points (and under certain circumstances give counterintuitive results) is that you'd probably have to throw a lot of natural science with the bathwater.
Actually, it's a bit simpler than that. Sciences, and scientific theories, can be easily identified by the property of falsifiability. If a theory makes coherent, testable predictions, and if the predictions can be tested empirically, then there's a basis for falsification. Economics doesn't have this property. Many natural sciences do. For example, anything having to do with evolution -- very specific, very testable, and excellent at resisting falsification. Not that surviving falsification is required to call something science -- failed theories and fields are scientific in a sense, certainly more so than those fields that never test their theories.
> ... whilst medics - like economists - are left with statistical tests, ad hoc explanations of confounding factors and a raft of exceptions that arguably falsify claims as uncontroversial as "drinking in excess is bad for your health".
Yes, but those aren't really falsifiable, are they? One can argue that a failed test like that is equivocal, not a basis for casting out the underlying theory. In a formal sense, that prevents their being called sciences.
I have to say about modern medicine that it's rapidly moving toward being evidence-based. Many clinical practices from years past have failed more rigorous efficacy trials and have been cast out as a result. So I would call it science on the basis that its theories and practices are open to falsification.