Some thoughts on evidence-based policy

I’m currently reading Les Mis (I have been for about 2 years – it’s half a million words long). A few months ago, Hugo described economists to me as “geologists of politics” (géologues de la politique). A pretty smart observation for 1862. It reminded me of a slightly more recent quip by Oswald Falk; telling his friend John Maynard Keynes that all he had really done was codify “the moral feeling of an age”.

Economic theory often follows political theory, no doubt, and policy can follow from either. But there are now calls in the UK for ‘evidence’ to enter the equation; most recently in eduction. In regard to economic and public policy, the argument is presumably that the story should go:

political theory > economic theory > evidence > policy.

A loose parallel in medicine might go:

medical theory > treatment > evidence > policy.

In medicine this is usually feasible, as human biology is relatively predictable. It is reasonably clear how medical questions can be answered; usually by randomised controlled trials and epidemiological studies. But is the step from theory to evidence as simple in public policy?

Evidence-based policy

In public policy, the story rarely goes as described above; evidence can fall anywhere in the schema – usually at the end. Evidence is retrospective, while policy is prospective. Human evolution is relatively slow, and what a drug does to a person now it is likely to do in 12 months’ time. Evidence collected in a trial is therefore largely applicable in the future. The same cannot be said for economies and societies. Evidence becomes heavily dependent on projections of what will happen in the future, and we (economists, humans) are notoriously bad at making predictions.

Evidence-based medicine (future edition)

Medicine is less dependent on projections, so evidence-based medicine is usually a safe bet. However, with the rise of personalised medicine, evidence-based medicine as we know it could be off the table. In personalised medicine, n=1. It won’t be possible to stratify trials by the four quadrillion different human genetic combinations; let alone different socio-economic indicators. Furthermore, some pressing questions are proving to be beyond the scope of evidence and prediction. For example, Richard Smith and Joanna Coast recently highlighted the limitations of evidence in antimicrobial resistance.

I’m all in favour of evidence-based medicine, as I’m not a moron! I’m also in favour of evidence-based policy wherever we can do it. But we need to acknowledge its limitations and avoid hubris whenever we do have ‘evidence’. Health economists live in a very evidence-based world, which is no bad thing, but we mustn’t restrict ourselves to it. We need to consider that, if we can’t find evidence of support for a policy (say, attaching a greater weight to end of life care), it may be that our theory is wrong.

When would the NHS have been created, had we waited for the evidence (or economic theory, for that matter)? How long can we wait for evidence in the case of antimicrobial resistance? In the long run we could all, quite literally, be dead. Sometimes it will be necessary to charge forward with policies that we know are right, but just can’t prove. The economists will add the veneer of theory later.

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