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    <title>Notebooks   </title>
    <link>http://bactra.org/notebooks</link>
    <description>Cosma's Notebooks</description>
    <language>en</language>

  <item>
    <title>Dynamic Stochastic General Equilibrium Models in Macroeconomics (DSGEs)</title>
    <link>http://bactra.org/notebooks/2012/02/19#dsges</link>
    <description>
&lt;P&gt;Pretend that the national economy consists of a single person, the
&quot;representative agent&quot;.  This agent owns all the goods, especially all the
capital goods, and does all the work in the economy.  The agent is greedy for
material consumption, and lazy.  To consume, which it likes, it must produce,
which is a matter of indifference, except that to produce it must work, which
it dislikes.  If it produces more now than it consumes, it can save the
difference as capital goods, which make its future labor more productive.
There are also shocks to &quot;technology&quot;, i.e., to how effectively it can use
capital to turn labor into consumption goods; rather bizarrely, these shocks
are both negative and positive, which means that it regularly forgets
productive technologies, and not because better replacements have come along.

&lt;P&gt;In addition to being greedy and lazy, the agent is is determined to act now
so as to maximize not present utility, but the discounted future stream of
utility at all times (since it is also immortal).  Fortunately, it is
incredibly foresighted, and knows the exact distribution of future shocks to
technology.  (This distribution is not changed by anything the agent does; or,
if you like, it always acts in such a way that its expectations are exactly
fulfilled.)  Possessing unlimited cognitive resources, it is easy for the agent
to solve the resulting &lt;a href=&quot;sequential-decisions.html&quot;&gt;dynamic programming
problem&lt;/a&gt; optimally.  This will not lead to a smooth pattern of production,
investment and consumption; if, for instance, there is a big negative shock to
technology, and shocks are persistent, it becomes rational to slack off now,
and enjoy leisure; extra work will be more rewarded later when the agent will
have remembered how to do stuff.  These fluctuations are, supposedly, the
fluctuations of the macroeconomy, the business cycle.

&lt;P&gt;I have sketched this sort of model in a deliberately hostile way, because I
think such things are remarkably silly.  But many very eminent economists
regard them very highly indeed.  Mostly I think this reflects badly on the
discipline of macroeconomics, but it does raise some interesting technical
problems, like:
	&lt;ul&gt;
	&lt;li&gt;How do people evaluate the fit of these models?
	&lt;li&gt;Do those evaluation methods make any sense?
	&lt;li&gt;How many of the parameters of these models are actually identifiable?
	&lt;li&gt;How much data would it take to estimate one of these models to a given degree of precision?
	&lt;li&gt;How much data would it take to detect that one of these models was wrong?
	&lt;li&gt;How well would these models fit in-sample if they were wrong about the structure of the economy?
	&lt;/ul&gt;

&lt;P&gt;(You might well ask &quot;where is the equilibrium, let alone the general
equilibrium, in a model with one agent and no trade?&quot;  You might very well ask
that.)

&lt;ul&gt;Recommended, examples and textbooks:
	&lt;li&gt;Bent Jesper Christensen and Nicholas M. Kiefer, &lt;cite&gt;Economic
Modeling and Inference&lt;/cite&gt; [Review: &lt;a href=&quot;../reviews/christensen-kiefer/&quot;&gt;An Optimal Path to a Dead End&lt;/a&gt;.]
	&lt;li&gt;David N. DeJong and Chetan Dave, &lt;cite&gt;Structural
Macroeconometrics&lt;/cite&gt; [&lt;a href=&quot;../weblog/algae-2011-01.html#dave-and-dave&quot;&gt;Review&lt;/a&gt;]
	&lt;li&gt;Finn E. Kydland and Edward C. Prescott, &quot;Time to Build and
Aggregate Fluctuations&quot;, &lt;cite&gt;Econometrica&lt;/cite&gt; &lt;strong&gt;50&lt;/strong&gt;
(1982): 1345--1370 [&lt;a href=&quot;http://www.jstor.org/stable/1913386&quot;&gt;JSTOR&lt;/a&gt;.  Pretty much the origins of the approach, and of &quot;real business cycle theory&quot;.]
	&lt;li&gt;Frank Smets and Rafael Wouters, &quot;Shocks and Frictions in US
Business Cycles: A Bayesian DSGE Approach&quot;, &lt;cite&gt;American Economic
Review&lt;/cite&gt; &lt;strong&gt;97&lt;/strong&gt; (2007): 586--606 [Perhaps the best-regarded
current DSGE of the US
economy.  &lt;a href=&quot;http://ideas.repec.org/p/ecb/ecbwps/20070722.html&quot;&gt;Preprint
version&lt;/a&gt;]
	&lt;/ul&gt;

&lt;ul&gt;Recommended, statistical aspects (in addition to the books by Christen and Kiefer, and by DeJong and Dave):
	&lt;li&gt;Marco Del Negro, Frank Schorfheie, Frank Smets and Rafael
Wouters, &quot;On the Fit of New Keynesian Models&quot;, &lt;a href=&quot;http://dx.doi.org/10.1198/073500107000000016&quot;&gt;&lt;cite&gt;Journal of Business and Economic Statistics&lt;/cite&gt; &lt;strong&gt;25&lt;/strong&gt; (2007): 123--162&lt;/a&gt; [Including discussion and reply]
	&lt;li&gt;Rochelle M. Edge and Refet S. Gurkaynak, &quot;How Useful are Estimated
DSGE Model Forecasts?&quot;, &lt;a href=&quot;http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1810075&quot;&gt;ssrn/1810075&lt;/a&gt; [Recommended for actually
going through the exercise of comparing out-of-sample forecasts, and including
simple baseline models.  But the methodological ideas here are suspect. It is
true that there is not much to predict about an in-control system, and what is
happening is largely random and so unpredictable, so that even the true model
would show low forecasting ability. The question however is why we are supposed
to think that the DSGE &lt;em&gt;does&lt;/em&gt; give us good information about
counterfactuals. If you could show that it had much better predictive
performance than baselines like constants or random walks
during &lt;em&gt;out-of-control&lt;/em&gt; periods, that would be something; but they
don't.]
	&lt;li&gt;Lars Peter Hansen and James J. Heckman, &quot;The Empirical
Foundations of Calibration&quot;, &lt;cite&gt;Journal of Economic Perspectives&lt;/cite&gt;
&lt;strong&gt;10&lt;/strong&gt; (1996): 87--104&lt;/a&gt; [Or, rather, the lack thereof.
&lt;a href=&quot;http://www.jstor.org/stable/2138285&quot;&gt;JSTOR&lt;/a&gt;]
	&lt;li&gt;Katarina Juselius and Massimo Franchi, &quot;Taking a DSGE Model to the
Data
Meaningfully&quot;, &lt;a href=&quot;http://dx.doi.org/10.5018/economics-ejournal.ja.2007-4&quot;&gt;&lt;cite&gt;Economics&lt;/cite&gt; &lt;strong&gt;1&lt;/strong&gt;
(2007): 4&lt;/a&gt; [There are places where Juselius and Franchi write as though a
VAR, or co-integrated VAR, were automatically
a &lt;a href=&quot;sufficienct-statistics.html&quot;&gt;sufficient statistic&lt;/a&gt; for any time
series.  This I think is mere minor carelessness; the general strategy here, of
seeing what implications the generative model has for phenomenological models,
and testing those implications, is quite sound (it's obviously close
to &lt;a href=&quot;indirect-inference.html&quot;&gt;indirect inference&lt;/a&gt;).  It is
particularly interesting to try to translate &lt;em&gt;specific&lt;/em&gt; pieces of the
generative model to specific observable hypotheses.  &amp;mdash; The fact that the
DSGE model is a miserable failure at matching the data is, of course, just a
bonus.]
	&lt;li&gt;Ivana Komunjer and Serena Ng, &quot;Dynamic Identification of
DSGE Models&quot; [Preprint available &lt;a href=&quot;http://econ.ucsd.edu/~ikomunje/respaper.htm&quot;&gt;via&lt;/a&gt; Prof. Komunjer]
	&lt;li&gt;Mark Watson, &quot;Measures of Fit for Calibrated Models&quot;, &lt;cite&gt;Journal
of Political Economy&lt;/cite&gt; &lt;strong&gt;101&lt;/strong&gt; (1993): 1011--1041
	&lt;/ul&gt;

&lt;ul&gt;Recommended, criticisms:
	&lt;li&gt;Willem Buiter, &lt;a href=&quot;http://blogs.ft.com/maverecon/2009/03/the-unfortunate-uselessness-of-most-state-of-the-art-academic-monetary-economics/&quot;&gt;&quot;The unfortunate uselessness of most `state of the art' academic monetary economics&quot;, &lt;cite&gt;Financial Times&lt;/cite&gt; 3 March 2009&lt;/a&gt; [The point about needing to &lt;em&gt;impose&lt;/em&gt; the transversality condition is particularly interesting]
	&lt;li&gt;Ricardo J. Caballero, &quot;Macroeconomics after the Crisis: Time to Deal with the Pretense-of-Knowledge Syndrome&quot;, &lt;a href=&quot;http://ssrn.com/abstract=1683617&quot;&gt;SSRN/1683617&lt;/a&gt;
	&lt;li&gt;David Colander,  Peter Howitt, Alan Kirman, Axel Leijonhufvud and Perry Mehrling, &quot;Beyond DSGE Models: Towards an Empirically-Based Macroeconomics&quot;
[&lt;a href=&quot;http://www.aeaweb.org/annual_mtg_papers/2008/2008_545.pdf&quot;&gt;PDF preprint&lt;/a&gt;]
	&lt;li&gt;Alan Kirman, &quot;Whom or What Does the Representative Individual
Represent?&quot;, &lt;cite&gt;Journal of Economic Perspectives&lt;/cite&gt; &lt;strong&gt;6&lt;/strong&gt;
(1992): 117--136
[Answer: No one and nothing; accordingly it &quot;deserves to be buried&quot;.  &lt;a href=&quot;http://www.jstor.org/pss/2138411&quot;&gt;JSTOR&lt;/a&gt;]
	&lt;li&gt;&lt;a href=&quot;http://artsci.wustl.edu/~morley/Main/Home.html&quot;&gt;James Morley&lt;/a&gt;, &quot;The Emperor Has No Clothes&quot;, &lt;cite&gt;Macro Focus&lt;/cite&gt; &lt;strong&gt;5:2&lt;/strong&gt; (March 2010) [&lt;a href=&quot;http://artsci.wustl.edu/~morley/emperor.pdf&quot;&gt;PDF&lt;/a&gt;]
	&lt;li&gt;Robert Solow, &quot;The State of
Macroeconomics&quot;, &lt;a href=&quot;http://dx.doi.org/10.1257/jep.22.1.243&quot;&gt;&lt;cite&gt;Journal
of Economic Perspectives&lt;/cite&gt; &lt;strong&gt;22&lt;/strong&gt; (2008): 243--249&lt;/a&gt; [&quot;the
claim that `modern macro' somehow has the special virtue of following the
principles of economic theory is tendentious and misleading... The other
possible defense of modern macro is that, however special it may seem, it is
justified empirically. This too strikes me as a delusion.&quot;]
	&lt;li&gt;Lawrence H. Summers, &quot;Some Skeptical Observations on
Real Business Cycle Theory&quot; [1986; &lt;a href=&quot;http://www.minneapolisfed.org/research/QR/QR1043.pdf&quot;&gt;PDF&lt;/a&gt;]
	&lt;/ul&gt;

&lt;ul&gt;Recommended, miscellaneous:
	&lt;li&gt;James K. Galbraith, Olivier Giovanni and Ann J. Russo, &quot;The
Fed's &lt;i&gt;Real&lt;/i&gt; Reaction Function: Monetary Policy, Inflation, Unemployment,
Inequality &amp;mdash; and Presidential Politics&quot; [Not directly about DSGEs, but
since so many of them incorporate some version of the Taylor rule, it amuses me
to think about writing one using this
instead.  &lt;a href=&quot;http://utip.gov.utexas.edu/&quot;&gt;University of Texas Inequality
Project&lt;/a&gt; &lt;a href=&quot;http://utip.gov.utexas.edu/papers/utip_42.pdf&quot;&gt;working
paper 42&lt;/a&gt;, 2007]
	&lt;li&gt;Herbert  Gintis, &quot;The Dynamics of General Equilibrium&quot;,
&lt;cite&gt;The Economic Journal&lt;/cite&gt; &lt;strong&gt;117&lt;/strong&gt; (2007): 1280--1309
[&lt;a href=&quot;http://www.umass.edu/preferen/gintis/General%20Equilibrium.pdf&quot;&gt;PDF reprint&lt;/a&gt; courtesy of Prof. Gintis]
	&lt;li&gt;Aapo Hyv&amp;auml;rinen, Kun Zhang, Shohei Shimizu, Patrik O. Hoyer, &quot;Estimation of a Structural Vector Autoregression Model Using Non-Gaussianity&quot;, &lt;a href=&quot;http://jmlr.csail.mit.edu/papers/v11/hyvarinen10a.html&quot;&gt;&lt;cite&gt;Journal of Machine Learning Research&lt;/cite&gt; &lt;strong&gt;11&lt;/strong&gt; 
(2010): 1709--1731&lt;/a&gt;
	&lt;li&gt;James Morley and Jeremy Piger, &quot;The Asymmetric Business Cycle&quot;,
&lt;a href=&quot;http://dx.doi.org/10.1162/REST_a_00169&quot;&gt;&lt;cite&gt;The Review of Economics and Statistics&lt;/cite&gt; &lt;strong&gt;94&lt;/strong&gt; (2012): 208--221&lt;/a&gt;
	&lt;/ul&gt;

&lt;ul&gt;To read:
	&lt;li&gt;George-Marios Angeletos and Jennifer La'O, &quot;Animal Spirits&quot;
[&lt;a href=&quot;http://econ-www.mit.edu/files/5322&quot;&gt;PDF&lt;/a&gt;.  From a quick
examination, epi-cycle adding --- or, rather, shock-adding.]
	&lt;li&gt;Jean Boivin and Marc P. Giannoni, &quot;DSGE Models in a Data-Rich Environment&quot; [&lt;a href=&quot;http://neumann.hec.ca/pages/jean.boivin/mypapers/dsgedr.pdf&quot;&gt;PDF preprint&lt;/a&gt;]
	&lt;li&gt;Fabio Canova and Luca Sala, &quot;Back to square one: identification issues in DSGE models&quot; [&lt;a href=&quot;http://www.econ.upf.edu/docs/papers/downloads/927.pdf&quot;&gt;PDF preprint&lt;/a&gt;]
	&lt;li&gt;David Colander (ed.), &lt;cite&gt;Post Walrasian Macroeconomics: Beyond the Dynamic Stochastic General Equilibrium Model&lt;/cite&gt; [&lt;a href=&quot;http://cambridge.org/9780521684200&quot;&gt;blurb&lt;/a&gt;]
	&lt;li&gt;Olivier Coibion and Yuriy Gorodnichenko, &quot;Strategic Interaction among Heterogeneous Price-Setters in an Estimated DSGE Model&quot;, &lt;a href=&quot;http://dx.doi.org/10.1162/REST_a_00102&quot;&gt;&lt;cite&gt;The Review of Economics and Statistics&lt;/cite&gt; &lt;strong&gt;93&lt;/strong&gt; (2011): 920--940&lt;/a&gt;
	&lt;li&gt;Roger E. A. Farmer, &lt;cite&gt;Expectations, Employment and Prices&lt;/cite&gt;
[&lt;a href=&quot;http://www.oup.com/us/catalog/general/subject/Economics/Labor/?view=usa&amp;ci=9780195397901&quot;&gt;&lt;/a&gt;]
	&lt;li&gt;Lance Taylor, &lt;cite&gt;Maynard's Revenge: The Collapse of Free Market Macroeconomics&lt;/cite&gt; [&lt;a href=&quot;http://www.hup.harvard.edu/catalog.php?isbn=9780674050464&quot;&gt;Blurb&lt;/a&gt;]
	&lt;/ul&gt;

&lt;ul&gt;To write:
	&lt;li&gt;Co-conspirators to be named later + CRS, &quot;Your Favorite DSGE
Sucks&quot;
	&lt;/ul&gt;
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