Consensus in macroeconomics

Paul Romer has continued the discussion he started, broadening it out from ‘mathiness’ to a more general discussion of how the subject is done. He describes what he regards as appropriate norms of science. The first few are I think uncontentious, but Stephen Williamson has taken exception to these two:

e) In our discussions, claims that are recognized by a clear plurality of members of the community by as being better supported by logic and evidence are the ones that are provisionally accepted as being true.

f) In judging what constitutes a “clear plurality,” we put more weight on the views of people who have more status in the community and are recognized as having more expertise on the topic.

Stephen writes:

This is absurd of course. We don't take polls to decide scientific merit. Indeed, revolutionary ideas - the ones that take the biggest steps toward Romerian truth - would be the ones that would fail, by this criterion.

I can understand that for those who typically work outside the mainstream, and indeed may be known for proposing new and challenging ideas, find this kind of talk threatening. Take it the wrong way, and it sounds like a recipe for conformity and stagnation.

I’m sure that is not what Paul intended, and I also think he is making an important point here. I suspect a natural scientist would see (e) and (f) as simple statements of how things are. In my experience natural scientists have a clear idea of what the “clear plurality” is on any particular issue, and are happy to admit it, even if they disagree with that plurality. There is nothing here that says academics cannot challenge the ideas of the “clear plurality”.

But why is it important to have an idea of what that plurality is and acknowledge it? I can think of three reasons. First, it presents an honest picture to those learning the discipline. Second, it is very important that policy makers are told which ideas are widely agreed and which are the views of a small minority. That does not stop policy makers going with the minority, but they should know what they are doing (as should voters). The public’s trust in economics might also increase as a result. Third, it helps the unity of the subject, mutual understanding and progress. It becomes clear why those who do not accept the views of the “plurality” disagree, and what they need to do to convince the plurality that they are wrong.

Convincing the majority that they are wrong is a strong motivational force for progress. In contrast, working within a small school of outsiders all of whom just know that the plurality is misguided, and as a result never bother to engage or keep up with it, is a recipe for stagnation. Before heterodox economists start hitting the keyboard, that also means that the plurality is open to unconventional ideas and do not just reject them because they are unusual or defy certain generally accepted norms.

It is for reasons like this that I have argued that it is wrong to say that macroeconomics is ‘flourishing’ simply because there are lots of different ideas/models out there. If there is no clear way of establishing which of these command general support and which are the insurgents, and what the insurgents need to do to overturn any consensus, then it is not clear how the discipline can progress.

This is all a bit abstract, so let me give an example from business cycle theory. Here there is, at present, a clear consensus theory, which is the New Keynesian model. I have been challenged on this in the past, but I would want to insist on it because I would attach a good deal of weight to those who are actually involved in business cycle stabilisation i.e. economists in central banks. (I’m not sure how important ‘status’ should be in Paul’s (f), but expertise is important, and having to put ideas into practice and responding to data all the time should count strongly.)

So when fiscal stimulus was used in 2009, those economists who opposed it should have said something like: I understand that temporary increases in government spending will raise output for given nominal rates in the dominant New Keynesian model, but I think that analysis is wrong because …. They should not have said, as some did, that fiscal stimulus was old fashioned nonsense. Whether they did this out of ignorance or contempt for the mainstream, it suggested that at least some prominent economists were not following the norms of science.

Why do central banks use New Keynesian models?

And more on whether price setting is microfounded in RBC models. For macroeconomists.

Why do central banks like using the New Keynesian (NK) model? Stephen Williamson says: “I work for one of these institutions, and I have a hard time answering that question, so it's not clear why Simon wants David [Levine] to answer it. Simon posed the question, so I think he should answer it.” The answer is very simple: the model helps these banks do their job of setting an appropriate interest rate. (I suspect because the answer is very simple this is really a setup for another post Stephen wants to write, but as I always find what Stephen writes interesting I have no problem with that.)

What is a NK model? It is a RBC model plus a microfounded model of price setting, and a nominal interest rate set by the central bank. Every NK model has its inner RBC model. You could reasonably say that these NK models were designed to help tell the central bank what interest rate to set. In the simplest case, this involves setting a nominal rate that achieves, or moves towards, the level of real interest rates that is assumed to occur in the inner RBC model: the natural real rate. These models do not tell us how and why the central bank can set the nominal short rate, and those are interesting questions which occasionally might be important. As Stephen points out, NK models tell us very little about money. Most of the time, however, I think interest rate setters can get by without worrying about these how and why questions.

Why not just use the restricted RBC version of the NK model? Because the central bank sets a nominal rate, so it needs an estimate of what expected inflation is. It could get that from surveys, but it also wants to know how expected inflation will change if it changes its nominal rate. I think a central banker might also add that they are supposed to be achieving an inflation target, so having a model that examines the response of inflation to the rest of the economy and nominal interest rate changes seems like an important thing to do.

The reason why I expect people like David Levine to at least acknowledge the question I have just answered is also simple. David Levine claimed that Keynesian economics is nonsense, and had been shown to be nonsense since the New Classical revolution. With views like that, I would at least expect some acknowledgement that central banks appear to think differently. For him, like Stephen, that must be a puzzle. He may not be able to answer that puzzle, but it is good practice to note the puzzles that your worldview throws up.

Stephen also seems to miss my point about the lack of any microfounded model of price setting in the RBC model. The key variable is the real interest rate, and as he points out the difference between perfect competition and monopolistic competition is not critical here. In a monetary economy the real interest rate is set by both price setters in the goods market and the central bank. The RBC model contains neither. To say that the RBC model assumes that agents set the appropriate market clearing prices describes an outcome, but not the mechanism by which it is achieved.

That may be fine - a perfectly acceptable simplification - if when we do think how price setters and the central bank interact, that is the outcome we generally converge towards. NK models suggest that most of the time that is true. This in turn means that the microfoundations of price setting in RBC models applied to a monetary economy rest on NK foundations. The RBC model assumes the real interest rate clears the goods market, and the NK model shows us why in a monetary economy that can happen (and occasionally why it does not). 

Two Anti-Keynesian myths

This is mainly of interest to economists, but given the importance of these issues, I have tried to write it in an accessible manner.

Stephen Williamson, in commenting on this post, remarks acidly that

“Part of what defines a Keynesian (new or old), is that a Keynesian thinks that his or her views are "mainstream," and that the rest of macroeconomic thought is defined relative to what Keynesians think - Keynesians reside at the center of the universe, and everything else revolves around them.”

In that post I was careful to distinguish between academic research and policy. Of course macroeconomists research many things, and only a minority are using New Keynesian models, and probably even some of those do not really need the New Keynesian bit. That is the great thing about abstraction. Working with what can be called ‘flex price’ models does not imply that you think price rigidity is unimportant, but instead that it can often be ignored if you want to focus on other processes. So in terms of research I talked about the significant divide being between mainstream and heterodox. In terms of research, mainstream macroeconomists talk the same language.

I used the term anti-Keynesian in the context of macroeconomic policy, and in this context I was not talking about academics, but the set of economists involved with macro policy. They could be academics, but they could be working for central banks, a finance ministry, or an international organisation like the IMF or OECD. For this group, I think we have good reason to believe that the large majority are not anti-Keynesian.

Just look, for example, at any central bank publication discussing recent movements in output. This will typically focus on movements in components of aggregate demand: consumption, investment etc. The reason is a belief that output in the short run is demand determined. That, for me, is the defining feature of Keynesian analysis. If you look at the core models used in central banks (which, unlike models used by academics, need to be ‘horses for all courses’) the same will be true.

Now Nick Rowe and David Glasner suggest that this view is not uniquely Keynesian - I could equally call it monetarist, for example. But what then are the criteria you will use to restrict the Keynesian set today? Different views about unconventional monetary policy? Different views about the efficacy of fiscal policy at the zero lower bound? This seems way too narrow. People have views about the relative merits of fiscal policy for all kinds of reasons, which may be very context specific, so this does not look like a good method of defining a label for economists today.  

Yet not everyone is a Keynesian using my deliberately broad definition. The only logical way to make sense of statements like those discussed here, for example, is to imagine we are in a world where output is determined from the supply side, so if one particular component of demand, like government spending on goods and services, goes down its impact on output will be offset by some means. That is an anti-Keynesian view. My first anti-Keynesian myth is that among economists involved with policy this is not a minority view.

The second myth is that all you need to justify this anti-Keynesian view is to observe that wages and prices move in response to booms and recessions. For example Roger Farmer points to negative inflation following the Great Depression. Language can be confusing here. As an analogy, suppose someone has been ill, and you ask them whether they are now better. Do you mean better than they were (but still ill), or completely recovered? For us to take an anti-Keynesian view, we do not just require prices to move, we require them to move by just the amount needed so that we can ignore demand. So, for example, in an open economy under fixed exchange rates, for a devaluation to have no demand impact requires prices to immediately rise by the same amount. Prices will begin to rise for sure, but ‘flexible prices’ means more than that.

If we take a simple closed economy, then ‘flexible prices’ is short for the real interest rate (nominal rates less expected inflation) always being at its ‘natural level’, which is the level that ensures demand matches supply. This immediately tells you that we are not just talking about price flexibility, but also monetary policy. Imagine in this economy there is a negative demand shock, caused by a fall in government spending. In this economy, the immediate impact is that firms will reduce output as well as prices. To offset this, the natural interest rate will fall to increase private consumption. Will the actual real interest rate do the same? This could happen without prices changing if the central bank cut nominal rates by exactly the required amount. It could happen without the central bank doing anything to nominal rates if expected inflation rose by exactly the required amount. Or it could be some combination of the two.

One justification for assuming that the real interest rate is always at its natural level is that monetary policy is super efficient, moving nominal rates to always offset the impact of demand shocks. For some reason this is not an argument anti-Keynesians usually make. The alternative justification is that, conditional on whatever monetary policy does, prices move by just the amount required to give you the expected inflation rate necessary to generate the natural real interest rate, and therefore offset the demand shock.

This becomes clear when nominal interest rates are stuck at the zero lower bound. In that case, the natural real interest rate is large and negative, but monetary policy cannot get there because nominal interest rates cannot be negative. For flexible prices to get you to that real rate you would need expected inflation to be significantly positive. (We now believe there is no independent Pigou effect (or real balance effect) that will save the day.) As Roger shows, actual inflation from 1929 to 1933 was persistently negative. One must presume that inflation expectations were also negative. So clearly although prices were moving, they were not moving in the way required for the anti-Keynesian view to hold. Far from casting doubt on the Keynesian story, falling prices during the Great Depression show how unrealistic the anti-Keynesian view is.

The New Classical Revolution: Technical or Ideological?

Paul Krugman: “The state of macro is, in fact, rotten, and will remain so until the cult that has taken over half the field is somehow dislodged”

The cult here is freshwater macro, which descends from the New Classical revolution. In response

Steve Williamson: “At the time, this revolution was widely-misperceived as a fundamentally conservative movement. It was actually a nerd revolution.” “What these people had on their side were mathematics, econometrics, and most of all the power of economic theory. There was nothing weird about what these nerds were doing - they were simply applying received theory to problems in macroeconomics. Why could that be thought of as offensive?”

The New Classical revolution was clearly anti-Keynesian, in the sense of Keynesian theory of the 1960s/70s, but was that simply because Keynesian theory was the dominant paradigm? As Williamson says, these guys were outsiders, and they wanted to revolutionise the discipline, which meant attacking the dominant theoretical framework of the time, which was Keynesian IS/LM.[1]

I have no particular expertise here: when this was all happening I viewed it from afar and with a lag, although perhaps that is also an advantage. But for what it is worth, I think there is some truth in what Stephen Williamson (SW) says. I certainly think that New Classical economists revolutionised macroeconomic theory, and that the theory is much better for it. Paul Krugman (PK) and I have disagreed on this point before. It was New Classical economists who recognised the importance of Muth’s rational expectations idea, and it is hard to imagine making sense of what the Fed has done this year without it.

But this is not where the real disagreement between PK and SW lies. The New Classical revolution became the New Neoclassical Synthesis, with New Keynesian theory essentially taking the ideas of the revolutionaries and adapting Keynesian theory to incorporate them. Once again, I believe this was a progressive change. While there is plenty wrong with New Keynesian theory, and the microfoundations project on which it is based, I would much rather start from there than with the theory I was taught in the 1970s. As SW says “Most of us now speak the same language, and communication is good.” What New Keynesian theory does is allow central banks to apply New Classical ideas in a way that is relevant to the task they have to perform, which is inflation control through demand management.

I think the difficulty that PK and I share is with those who in effect rejected or ignored the New Neoclassical Synthesis. I can think of no reason why the New Classical economist as ‘revolutionary nerd’ should do this, which suggests that SW’s characterisation is only half true. Everyone can have their opinion about particular ideas or developments, but it is not normal to largely ignore what one half of the profession is doing. Yet that seems to be what has happened in significant parts of academia.

SW likes to dismiss PK as being out of touch with current macro research. Lets look at the evidence. PK was very much at the forefront of analysing the Zero Lower Bound problem, before that problem hit most of the world. While many point to Mike Woodford’s Jackson Hole paper as being the intellectual inspiration behind recent changes at the Fed, the technical analysis can be found in Eggertsson and Woodford, 2003. That paper’s introduction first mentions Keynes, and then Krugman’s 1998 paper on Japan. Subsequently we have Eggertsson and Krugman (2010), which is part of a flourishing research programme that adds ‘financial frictions’ into the New Keynesian model. You would not think of suggesting that PK is out of touch unless you are in effect dismissing or marginalising this whole line of research.[2]

I would not describe the state of macro as rotten, because that appears to dismiss what most mainstream macroeconomists are doing. I would however describe it as suffering from two unhelpful biases. The first is methodological: too much of an obsession with microfoundation purity, and too little interest in evidence. The second is ideological: a legacy of the New Classical revolution that refuses to acknowledge the centrality of Keynesian insights to macroeconomics. These biases are a serious problem, partly because they can distort research effort, but also because they encourage policy makers to make major mistakes.[3]
   



[1] The clash between Monetarism and Keynesianism was mostly a clash about policy: Friedman used the Keynesian theoretical framework, and indeed contributed greatly to it.

[2] It may be legitimate to suggest someone is out of touch with macro theory if they make statements that are just inconsistent with mainstream theory, without acknowledging this to be the case. The example that most obviously comes to mind is statements like these, about the impact of fiscal policy.

[3] In the case of the UK, a charitable explanation for the Conservative opposition to countercyclical fiscal policy and their embrace of austerity was that they believed conventional monetary policy could always stabilise the economy. If they had taken on board PK’s analysis of Japan, or Eggertsson and Woodford, they would not have made that mistake.

Mistaking models for reality

In a recent post, Paul Krugman used a well known Tobin quote: it takes a lot of Harberger triangles to fill an Okun gap. For non-economists, this means that the social welfare costs of resource misallocations because prices are ‘wrong’ (because of monopoly, taxation etc) are small compared to the costs of recessions. Stephen Williamson takes issue with this idea. His argument can be roughly summarised as follows:

1) Keynesian recessions arise because prices are sticky, and therefore 'wrong', so their costs are not fundamentally different from resource misallocation costs.

2) Models of price stickiness exaggerate these costs, because their microfoundations are dubious.

3) If the welfare costs of price stickiness were significant, why are they not arbitraged away?

I’ve heard these arguments, or variations on them, many times before.[1] So lets see why they are mistaken, taking the points in roughly reverse order.

Keynesian recessions arise because of deficient demand. If you want to think of this as being because some price is wrong, in my view that price is the real interest rate. Now flexible wages and prices might get you the right real interest rate, either because they encourage monetary policy to do the right thing (by changing inflation), or because a particular monetary policy combines with inflation expectations to generate the appropriate real interest rate. However when nominal interest rates hit zero and there are inflation targets, flexible prices may not be enough (as argued here), so there may be no flexible price solution that gets rid of the costs of recession. At the very least, that suggests that recessions are a bit different from, say, the costs of monopoly or distortionary taxation. It also tells you why they cannot be arbitraged away by the actions of individuals.(See also Nick Rowe on this.)

What we have in a recession is a coordination problem. If everyone were to spend more, the additional output would generate incomes that matched the spending. If monetary policy cannot induce that coordination, then individuals could try and persuade someone with a great deal of spending power who could borrow freely and very cheaply to embark on additional spending. The obvious someone is the government, and the real puzzle is why governments have been so reluctant to arbitrage away recessions in this way.  

The second point is horribly wrong, and it explains the title of this post. The problem with modelling price rigidity is that there are too many plausible reasons for this rigidity - too many microfoundations. (Alan Blinder’s work is a classic reference here.) Microfounded models typically choose one for tractability. It is generally possible to pick holes in any particular tractable story behind price rigidity (like Calvo contracts). But it does not follow that these models of Keynesian business cycles exaggerate the size of recessions. It seems much more plausible to argue completely the opposite: because microfounded models typically only look at one source of nominal rigidity, they underestimate its extent and costs.

I could make the same point in a slightly different way. Lets suppose that we do not fully understand what causes recessions. What we do understand, in the simple models we use, accounts for small recessions, but not large ones. Therefore, large recessions cannot exist. The logic is obviously faulty, but too many economists argue this way. There appears to be a danger in only ‘modelling what we understand’ that modellers can go on to confuse models with reality.

Lets move from wage and price stickiness to the major cost of recessions: unemployment. The way that this is modelled in most New Keynesian set-ups based on representative agents is that workers cannot supply as many hours as they want. In that case, workers suffer the cost of lower incomes, but at least they get the benefit of more leisure. Here is a triangle maybe (see Nick Rowe again.) Now this grossly underestimates the cost of recessions. One reason is  heterogeneity: many workers carry on working the same number of hours in a recession, but some become unemployed. Standard consumer theory tells us this generates larger aggregate costs, and with more complicated models this can be quantified. However the more important reason, which follows from heterogeneity, is that the long term unemployed typically do not think that at least they have more leisure time, so they are not so badly off. Instead they feel rejected, inadequate, despairing, and it scars them for life. Now that may not be in the microfounded models, but that does not make these feelings disappear, and certainly does not mean they should be ignored.

It is for this reason that I have always had mixed feelings about representative agent models that measure the costs of recessions and inflation in terms of the agent’s utility.[2] In terms of modelling it has allowed business cycle costs to be measured using the same metric as the costs of distortionary taxation and under/over provision of public goods, which has been great for examining issues involving fiscal policy, for example. Much of my own research over the last decade has used this device. But it does ignore the more important reasons why we should care about recessions. Which is perhaps OK, as long as we remember this. The moment we actually think we are capturing the costs of recessions using our models in this way, we once again confuse models with reality.




[1] A classic example comes from Robert Lucas. This includes the rather unfortunate statement that the “central problem of depression prevention has been solved”, but I don’t think that should be used as evidence against the more substantive claim of the paper, which is that the gains from stabilising the business cycle are relatively small. This assertion has been criticised even if we stick with New Keynesian representative agent models (see this paper by Canzoneri, Cumby and Diba), but the problems I outline below are more fundamental.

[2] For non-economists: twenty years ago most Keynesian analysis measured the success of policy (social welfare) by how well it stabilised inflation and the output gap, and the relative importance of inflation compared to output was a ‘choice for policy makers’. Since work by Michael Woodford, a similar measure of social welfare can be derived from the utility of individual agents, often using pages of maths, but the importance of output compared to inflation is then a function of this utility and the model’s structure and parameters.