When David Vines asked me to contribute to a OXREP (Oxford Review of Economic Policy) issue on “Rebuilding Macroeconomic Theory”, I think what he hoped I would write on how the core macro model needed to change to reflect macro developments since the crisis with a particular eye to modelling the impact of fiscal policy. That would be an interesting paper to write, but I decided fairly quickly that I wanted to say something that I thought was much more important.
In my view the biggest obstacle to the advance of macroeconomics is the hegemony of microfoundations. I wanted at least one of the papers in the collection to question this hegemony. It turned out that I was not alone, and a few papers did the same. I was particularly encouraged when Olivier Blanchard, in blog posts reflecting his thoughts before writing his contribution, was thinking along the same lines.
I will talk about the other papers when more people have had a chance to read them. Here I will focus on my own contribution. I have been pushing a similar line in blog posts for some time, and that experience suggests to me that most macroeconomists working within the hegemony have a simple mental block when they think about alternative modelling approaches. Let me see if I can break that block here.
Imagine a DSGE model, ‘estimated’ by Baynesian techniques. To be specific, suppose it contains a standard intertemporal consumption function. Now suppose someone adds a term into the model, say unemployment into the consumption function, and thereby significantly improves the fit of the model. It is not hard to think why the fit significantly improves: unemployment could be a proxy for the uncertainty of labour income, for example. The key question becomes which is the better model with which to examine macroeconomic policy: the DSGE or the augmented model?
A microfoundations macroeconomist will tend to say without doubt the original DSGE model, because only that model is known to be theoretically consistent. (They might instead say that only that model satisfies the Lucas critique, but internal consistency is the more general concept.) But an equally valid response is to say that the original DSGE model will give incorrect policy responses because it misses an important link between unemployment and consumption, and so the augmented model is preferred.
There is absolutely nothing that says that internal consistency is more important than (relative) misspecification. In my experience, when confronted with this fact, some DSGE modellers resort to two diversionary tactics. The first, which is to say that all models are misspecified, is not worthy of discussion. The second is that neither model is satisfactory, and research is needed to incorporate the unemployment effect in a consistent way.
I have no problem with that response in itself, and for that reason I have no problem with the microfoundations project as one way to do macroeconomic modelling. But in this particular context it is a dodge. There will never be, at least in my lifetime, a DSGE model that cannot be improved by adding plausible but potentially inconsistent effects like unemployment influencing consumption. Which means that, if you think models that are significantly better at fitting the data are to be preferred to the DSGE models from whence they came, then these augmented models will always beat the DSGE model as a way of modelling policy.
What this question tells you is that there is an alternative methodology for building macroeconomic models that is not inferior to the microfoundations approach. This starts with some theoretical specification, which could be a DSGE model as in the example, and then extends it in ways that are theoretically plausible and which also significantly improve the model’s fit, but which are not formally derived from micofoundations. I call that an example within the Structural Econometric Model (SEM) class, and Blanchard calls it a Policy Model.
An important point I make in my paper is that these are not competing methodologies, but instead they are complementary. SEMs as I describe them here start from microfounded theory. (Of course SEMs can also start from non-microfounded theory, but the pros and cons of that is a different debate I want to avoid here.) As a finished product they provide many research agendas for microfoundation modelling. So DSGE modelling can provide the starting point for builders of SEMs or Policy Models, and these models when completed provide a research agenda for DSGE modellers.
Once you see this complementarity, you can see why I think macroeconomics would develop much more rapidly if academics were involved in building SEMs as well as building DSGE models. The mistake the New Classical Counter Revolution made was to dismiss previous ways of modelling the economy, instead of augmenting these ways with additional approaches. Each methodology on its own will develop much more slowly than the two combined. Another way of putting it is that research based on SEMs is more efficient than the puzzle resolution approach used today.
In the paper, I try to imagine what would have happened if the microfoundations project had just augmented the macroeconomics of the time (which was SEM modelling), rather than dismissing it out of hand. I think we have good evidence that active complementarity between SEM and microfoundations modelling would have investigated in depth links between the financial and real sectors before the financial crisis. The microfoundations hegemony chose the wrong puzzles to look at, deflecting macroeconomics from the more important empirical issues. The same thing may happen again if the microfoundations hegemony continues.