I don't blog much about macroeconomics methodology debates that much anymore, but every once in a while it's still fun to wade back in.
Mark Thoma wrote a column in the Fiscal Times in which he explained where he thought macroeconomics went wrong before the 2008 crisis. Some key excerpts:
There are good reasons to be critical of the rational expectations, dynamically optimizing, representative agent approach that underlies modern macroeconomic models. For example, the representative agent approach makes it difficult to study financial markets. At least two agents with different views about the future price of a financial asset are needed before we can even begin to model markets for financial assets, financial intermediation, and other key elements of the financial sector...
[M]acroeconomists, for the most part, did not think questions about financial meltdowns were worth asking, so why bother with those theoretical complications? The financial collapse problem had been overcome, or so some macroeconomists thought.
Nobel prize winning economist Robert Lucas, for example, in his 2003 presidential address to the American Economic Association famously claimed that the “central problem of depression-prevention has been solved.”Josh Hendrickson, whose blog is called "The Everyday Economist" but whose Twitter handle is @RebelEconProf, decided not to be a rebel every day, and came to the defense of pre-crisis macro, Lucas, etc. Josh makes some good points and some unconvincing points.
Here is a really good point:
Suppose there is some exogenous shock to the economy. There are two possible scenarios. In Scenario 1, macroeconomists have models that describe how the shock will affect the economy and the proper policy response. In Scenario 2, macroeconomists have no such models.
In Scenario 1, we avoid a severe recession. In Scenario 2, we could possibly have a severe recession...Given [macro critics'] logic, the only time that we would have a severe recession is when macroeconomists are ill-prepared to explain what is likely to happen and to provide a policy response.In other words, our perceptions of the failures of macroeconomics are hugely influenced by selection bias. True! How many more crises would we have had without the models we have developed? Maybe none, or maybe some. How useless macro has or hasn't been depends on the crises we avoided, not just the ones we failed to avoid.
Here is a point that is somewhat less convincing:
Thoma argues that the reason that we lacked a proper policy response to severe recessions was because people like Robert Lucas thought we didn’t need to study such things. However, this is a very uncharitable view of what Lucas stated in his lecture (read it here)...when Lucas says that the depression-preventing policy problem has been solved, he actually provides examples of what he means by depression-prevention policies. According to Lucas preventing severe recessions occurs when policymakers stabilize the monetary aggregates and nominal spending. This is essentially the same depression-prevention policies advocated by Friedman and Schwartz. Given that view, he doesn’t think that trying to mitigate cyclical fluctuations will have as large of an effect on welfare as supply-side policies.Lucas' speech, in other words, is a sort of old-monetarist variant of the Great Moderation hypothesis, which was very common among macroeconomists at the time. But the Great Moderation turned out to be illusionary, and that's Thoma's whole point. It may be unfair to single out Lucas for an idea that most macroeconomists shared at the time, but he is a very famous and influential guy, after all.
Josh then makes the odd point that since we didn't actually adopt the policy that Lucas claims we did adopt (stabilization of monetary aggregates), Lucas wasn't wrong. That's just too weird of a point, so I'll skip it.
Josh then makes another good point:
Thoma argues...that economists spent far too little time trying to explain the Great Moderation. This simply isn’t true. John Taylor, Richard Clarida, Mark Gertler, Jordi Gali, Ben Bernanke, and myself all argued that it was a change in monetary policy that caused the Great Moderation.This is true. I think Mark probably misspoke; what he probably meant was not that economists didn't try to explain the Great Moderation, but that they didn't question the Moderation's stability as suspiciously as they might have.
Josh then makes another unconvincing point:
Similarly, his criticism that economists simply didn’t care enough about financial markets is unfounded. Townsend’s work on costly state verification and the follow-up work by Steve Williamson, Tim Fuerst, Charles Carlstrom, Ben Bernanke, Mark Gertler, Simon Gilchrist, and others represents a long line of research on the role of financial markets. Carlstrom and Fuerst and well as Bernanke, Gertler, and Gilchrist found that financial markets can serve as a propagation mechanism for other exogenous shocks. These frameworks were so important in the profession that if you pick up Carl Walsh’s textbook on monetary economics there is an entire chapter dedicated to this sort of thing. It is therefore hard to argue the profession didn’t take financial markets seriously.This is the idea that "there exist papers on X" means "the profession took X seriously". But that doesn't seem right to me. After all, there is nothing limiting the topics on which macroeconomists write papers, and there is every incentive for them to write papers imagining any and every conceivable phenomenon. So there will, in general, be a macro paper on any topic. But it is impossible for the profession to simultaneously take every topic seriously, so we need a better criterion than the existence of papers.
In particular, the claim that macroeconomists thought enough about financial shocks and frictions before the crisis seems to conflict with the huge outpouring of work on financial shocks and frictions since the crisis. If macroeconomists were clued in to the dangers of financial stuff before the crisis, why all the new models?
Josh then misunderstands one of Thoma's criticisms:
The same thing can be said about representative agent models. Like Thoma, I share the opinion that progress means moving away from representative agents. However, the profession began this process long ago. While the basic real business cycle model and the New Keynesian model still have representative agents, there has been considerable attention paid to heterogeneous agent models.But Thoma was talking about heterogeneous beliefs. The models Josh is talking about incorporate heterogeneous wealth, productivity, etc., but not heterogeneous beliefs. There are lots of heterogeneous-belief models in the finance literature (see here for some of them). But macro models mostly continue to adhere to the rational-expectations framework advocated by Lucas, or occasionally a representative-agent version of a learning model, neither of which incorporates heterogeneous beliefs. I say "mostly" because I haven't seen any recent macro models that include heterogeneous beliefs, but Rule 1 of macro is "There is a macro paper on any topic."
Anyway, Josh makes some good points, but he also goes pretty soft on the profession and its leading thinkers regarding the pre-crisis consensus, which really did downplay the importance of finance, and really did avoid thinking about heterogeneous beliefs.