DSGE models — worse than useless

21 Jul, 2019 at 14:35 | Posted in Economics | 1 Comment

If you want absolute truth then you must look to pure mathematics or religion, but certainly not to science … Science is all about possibilities. We propose theories, conjectures, hypotheses and explanations. We collect evidence and data, and we test the theories against this new evidence … It’s the very essence of science that its conclusions can change, that is, that its truths are not absolute. The intrinsic good sense of this is contained within the remark reportedly made by the eminent economist John Maynard Keynes, responding to the criticism that he had changed his position on monetary policy during the 1930s Depression: “When the facts change, I change my mind. What do you do, sir?”

DSGE models are worse than useless — and still, mainstream economists seem to be überimpressed by the ‘rigour’ brought to macroeconomics by New-Classical-New-Keynesian DSGE models and its rational expectations and microfoundations!

It is difficult to see why.

‘Rigorous’ and ‘precise’ DSGE models cannot be considered anything else than unsubstantiated conjectures as long as they aren’t supported by evidence from outside the theory or model. To my knowledge, no decisive empirical evidence has been presented.

Proving things ‘rigorously’ in DSGE models is at most a starting-point for doing an interesting and relevant economic analysis. Forgetting to supply export warrants to the real world makes the analysis an empty exercise in formalism without real scientific value.

Mainstream economists think there is a gain from the DSGE style of modelling in its capacity to offer the one and only structure around which to organise discussions. To me, that sounds more like a religious theoretical-methodological dogma, where one paradigm rules in divine hegemony. That’s not progress. That’s the death of economics as a science.

As David Hand tells us — building models based on questionable ontological or epistemological assumptions may be fine in mathematics and religion, but it certainly is not science.