Saturday, July 28, 2012

A Critique of the Lucas Critique

The blogosphere, it seems recently, has been particularly rich in blogoyakking (sp?) concerning microfoundations. Wren-Lewis, Noah Smith, Krugman, Rowe, Plosser, and others just in the week prior to this post.

And this has caused a persistent itch of mine to clamor for scratching. Here goes.

The Lucas critique is fairly widely acknowledged to have at least exacerbated the trend toward insisting on microfoundations in macro theory, and thus the rise of New Keynesian Dynamic Stochastic General Equilibrium models. You know, representative agents showing rational expectations over generations, and all such things, reacting to policy changes. Which individual behaviors we can, more or less simply, just add up in order to understand the effects on the macro economy.

For those needing a brief review on "the" critique, Wikipedia is actually not bad, which I summarize. Lucas said:
"Given that the structure of an econometric model consists of optimal decision rules of economic agents, and that optimal decision rules vary systematically with changes in the structure of series relevant to the decision maker, it follows that any change in policy will systematically alter the structure of econometric models."
This is from his 1976 paper.

And the Wiki article summarizes the implications:
"The Lucas critique suggests that if we want to predict the effect of a policy experiment, we should model the "deep parameters" (relating to preferences, technology and resource constraints) that govern individual behavior. We can then predict what individuals will do, taking into account the change in policy, and then aggregate the individual decisions to calculate the macroeconomic effects of the policy change."
Thus, Bortis-style classical-Keynesianism was pretty much denuded: at best macro policy is effectively toothless, since that pesky agent will simply react to neutralize the policy actions;  and/or react so that the empirical regularities we were observing and making policy on will change. So we need to focus on micro and get that "right," the best we can do. The domination of Methodological Individualism on economic practice was on the rise.

I think Lucas got part of the diagnosis correct: individuals do react to macro policy changes but only indirectly. And he got most of it wrong. For the most part individual behaviors do not  directly change the  structure of the time series, but it is the change in the structure of the time series that changes individual behavior. Aggregate demand falls due to some shock - asset deflation, price shocks, war, pestilence, loss of income due to technology or offshoring. Producers then decrease output, and fire their workers.

This shock mechanism does induce individually optimizing behavior on the part of the business owner, given that what he optimizes is his profit function into which his production output enters.

For the newly unemployed person, since s/he no longer has a source of income, one can stretch and say that reducing consumption is individually optimizing at least of negative deviations from the budget. Of course this mechanism has it's own brutal zero lower bound - subsistence.  And does nothing to maximize utility.

Notice, no macro policy change is required here to start a recession or the recent depression; all we need is a sufficient shock to the system to start the negative feedback cycles rolling along.

We classical-Keynesian macroeconomists characterize these mechanisms as showing the fallacy of composition; the canonical principles of economics example is the paradox of thrift. You cannot use added-up individually optimizing behaviors to determine what is going to happen to the macro economy.

The reason is clear: emergent properties at the macro level have a life of their own. And its is these emergent properties like recessions and unemployment that directly affect the behavior of the economic person. I take here the strong version of emergent: a property or behavior at the aggregate level which cannot be observed or predicted at the individual level.

We do have methods that attempt to model this: the Keynesian aggregate expenditure model, but that is static. Dynamic macro econometric models, but those are difficult, and maybe it was because of these difficulties that the Lucas critique was so successful in attacking them.

I propose two things to restore the dominating importance of emergent macro properties on economic behavior. One is a recommitment to econometric modelling. Ever increasing data and increasingly better tools will continually improve modelling and forecasting results.

The other is a methodology that is vastly underused in economics, but widely used in various other sciences: network system analysis based on the mathematical theory of graphs. These methods lets us directly measure and model emergent dynamic behaviors from groups, like the individuals in an economy. No added up methodological individualism required; no agent-based model needed. Observe, model, and predict directly at the macro level.

While I believe empirical models, properly done, are fundamental to understanding and policy, network models provide us with a dynamic theory, emergent macro behaviors, that  support our correct Keynesian beliefs that it is the macro foundations of micro behavior that matter, not the other Lucasian way around.


7 comments:

  1. Hey, be careful with the use of classical and classical-Keynesian. When you say "we classical macroeconomists" you mean I assume in the old sense of classical political economy, but with Keynesian-Kaleckian features (i.e. principle of effective demand), which I call, following Bortis classical-Keynesian. However, your use of classical Keynesianism seems to suggest that you were talking of the Old Keynesians of the neoclassical synthesis, whose version of Keynesianism was denuded by the Lucas critique.

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  2. point taken. I meant the Bortis school.

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    1. If you meant classical-Keynesian in the sense that Bortis and I use it then, I would disagree that the Lucas critique had any effect, let alone being denuded, on policy advice. Note that the Lucas critique is terrible for Old Keynesians and New Keynesians, since agents imperfect reactions are central to obtain the Keynesian results. That is not the case with the properly founded Sraffian Keynesians. For example, a government expansion that expands demand, leads through the accelerator to increased pirvate investment, and expectations or agents reactions are fundamentally irrelevant from a classical-Keynesian stance.

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  3. "For the most part individual behaviors do not directly change the structure of the time series, but it is the change in the structure of the time series that changes individual behavior. Aggregate demand falls due to some shock - asset deflation, price shocks, war, pestilence, loss of income due to technology or offshoring. Producers then decrease output..."

    Sweet.

    Regarding the reasons AD falls, to me the most neglected (and likely the most important) cause is that monetary balances shift over time as a result of individual behaviors and economic policies. Shifting monetary balances, neglected, eventually become burdensome debt and income inequality and excessive financialization and such; and these "innocent" shifts -- not recognized as shocks, perhaps because they are not shocks -- are more likely the root cause of troubles than asset deflation, war, and whatever, together.

    What I describe may be considered a macro shock.

    "Notice, no macro policy change is required here to start a recession or the recent depression; all we need is a sufficient shock to the system to start the negative feedback cycles rolling along."

    Yes, all we need is that; or even just an innocent shift, sufficiently ignored.

    Good post.
    Art

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    1. Art,
      Nice comments with which I certainly agree. This post also caught my attention because I'm currently reading a book on the same topic by Paul Ormerod, titled Positive Linking: How Networks Can Revolutionize the World. It's a fascinating read on the topic that I highly recommend.

      Steve,
      Great post and good to see more economists incorporating network effects into models and trying to bring back the importance of emergence. Definitely deserving of a link on my site, which I posted here http://bit.ly/Mvaboa.

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  4. I think that Pasinetti, who, by the way, uses the term "Cambridge Keynesians"has wrotte widely about the macrofundations of microeconomics.

    Nice post.
    Regards.

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    1. Yep, but some Cambridge Keynesians, like Joan Robinson, have a tendency to like Cambridge equation growth models instead of the supermultiplier, which I think is the way to extend Keynes' Principle of Effective Demand to the long run. That's why I like Bortis' term, classical-Keynesians.

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