Krugman Apologises!

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Sor­ry, that was a belat­ed April Fool’s joke. He has­n’t, of course—though there has been an apol­o­gy of sorts from Nick Rowe, which is duly not­ed and accept­ed.

The best Krug­man could man­age is the fol­low­ing update to his orig­i­nal dia­tribe “Oh My, Steve Keen Edi­tion”:

Update update: Ah, so Keen did­n’t mean DSGE — a term that refers only to New Key­ne­sian mod­els — when he said DSGE; he meant New Clas­si­cal, which he some­how regards as the under­ly­ing prin­ci­ples for mod­els that aren’t New Clas­si­cal at all. OK. Any­way, enough of that. I’m all for lis­ten­ing to heretics when they offer insights I can use, but I’m not find­ing that at all in this con­ver­sa­tion, just word games and con­tin­u­al insis­tence that the mem­bers of the sect have insights denied to us less­er mor­tals. Time to move on.

Gee, thanks Paul. So I’m play­ing word games, am I—and you’re not? Let’s take a clos­er look.

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Marking Krugman

Paul, your com­pre­hen­sion of my piece failed on at least two counts.

Fig­ure 1: Krug­man’s Last Word

First­ly, in the excerpt you quote, I refer to “under­ly­ing prin­ci­ples to the DSGE mod­els that now dom­i­nate Neo­clas­si­cal macro­eco­nom­ics”. Some­how you read that as being a state­ment about “about New Key­ne­sian mod­els”.

No it was­n’t Paul: I was refer­ring to the gen­er­al class of post-IS-LM neo­clas­si­cal mod­els, which includes the “Fresh­wa­ter” New Clas­si­cal mod­els about which you have made such a song and dance in the past—contrasting their unre­al­i­ty and con­ser­vatism with your real­is­tic pro­gres­sive­ness. Remem­ber “Fresh­wa­ter Rage”, “How did Econ­o­mists get it so wrong?” or “Dis­agree­ment among econ­o­mists”? You might dis­like them Paul, but they’re your Neo­clas­si­cal cousins, and it was their “pure” the­o­ry, which forms the foun­da­tion for your NK mod­els, to which I referred in that excerpt.

Yes, I know that Mark Thoma claimed in a Tweet that New Clas­si­cal mod­els weren’t DSGE models—and that by impli­ca­tion, DSGE was reserved for NK mod­els exclu­sive­ly and there­fore my Fail grade was wrong. I’ll get to that lat­er.

Sec­ond­ly, direct­ly below the sec­tion you quote, I con­tin­ued as fol­lows:

If that were actu­al­ly the real world, then not only would there not be a cri­sis now, there would nev­er have been a Great Depres­sion either—and reces­sions would sim­ply be minor sta­tis­ti­cal­ly unpre­dictable but inevitable events when the major­i­ty of shocks hit­ting the econ­o­my were neg­a­tive, and they would rapid­ly be resolved by adjust­ments to rel­a­tive prices (wages includ­ed, of course).

So econ­o­mists like Krugman—who describe them­selves as “New Keynesians”—have tweaked the base case to derive mod­els that “ape” real-world data, with “sticky” prices rather than per­fect­ly flex­i­ble ones, “fric­tions” that slow down quan­ti­ty adjust­ments, and imper­fect com­pe­ti­tion to gen­er­ate less-than-opti­mal social out­comes.

This is Ptole­ma­ic Eco­nom­ics: take a mod­el that is utter­ly unlike the real world, and which in its pure form can’t pos­si­bly fit real world data, and then add “imper­fec­tions” so that it can appear to do so.

So Paul, not only did I dis­tin­guish between NC mod­els and NK ones, I even men­tioned you by name in that sec­tion as some­one who has added imper­fect com­pe­ti­tion, sticky prices and so on to that base NC mod­el. And yet you implied that I was a moron who did­n’t even know that NK mod­els include imper­fect com­pe­ti­tion, sticky prices and so on—and you won­der why you got a Fail?

Oh all right, yes I’ll con­sid­er Thoma’s argu­ment. I see that’s what you’re claim­ing in your attempt to weasel out of an apol­o­gy:

so Keen did­n’t mean DSGE — a term that refers only to New Key­ne­sian mod­els — when he said DSGE

Fig­ure 2: Thoma’s Tweet

So you and Thoma believe that DSGE mod­els exclu­sive­ly refer to NK mod­els? Frankly I think that’s like a wrin­kled pea claim­ing that it’s unre­lat­ed to a smooth one: they’re still both peas. And the Wikipedia entry on DSGE mod­els—which I’m sure has been checked over pret­ty care­ful­ly by fans of Neo­clas­si­cal economics—makes no such dis­tinc­tion. In fact, it treats RBC/NC and NK as schools of DSGE mod­el­ling, pre­cise­ly as I do:

Schools of DSGE mod­el­ing

At present two com­pet­ing schools of thought form the bulk of DSGE mod­el­ing.[1]

Real busi­ness cycle (RBC) the­o­ry builds on the neo­clas­si­cal growth mod­el, under the assump­tion of flex­i­ble prices, to study how real shocks to the econ­o­my might cause busi­ness cycle fluc­tu­a­tions. The paper of Kyd­land and Prescott (1982) is often con­sid­ered the start­ing point of RBC the­o­ry and of DSGE mod­el­ing in gen­er­al.[2] The RBC point of view is sur­veyed in Coo­ley (1995).

New-Key­ne­sian DSGE mod­els build on a struc­ture sim­i­lar to RBC mod­els, but instead assume that prices are set by monop­o­lis­ti­cal­ly com­pet­i­tive firms, and can­not be instan­ta­neous­ly and cost­less­ly adjust­ed. The paper that first intro­duced this frame­work was Rotem­berg and Wood­ford (1997). Intro­duc­to­ry and advanced text­book pre­sen­ta­tions are giv­en by Galí (2008) and Wood­ford (2003). Mon­e­tary pol­i­cy impli­ca­tions are sur­veyed byClar­i­daGalí, and Gertler (1999).” (Wikipedia Entry)

So I won’t accept Thoma’s excuse for your behaviour—and nor do some of his own fol­low­ers, judg­ing by his sub­se­quent Tweets.

Fig­ure 3: Thoma’s sub­se­quent Tweets

You should also read that Wikipedia entry, by the way—it includes some crit­i­cisms of DSGE mod­el­ling by your senior Robert Solow that you clear­ly haven’t paid atten­tion to (Robert M. Solow, 2003, 2001, 2008). I know you don’t like read­ing what oth­er peo­ple write—“I Don’t Care” I think you said—but that’s why you make mis­takes like the one you’ve made here. Since I know from your past form that my advice here is prob­a­bly falling on deaf ears, here’s Solow as quot­ed in the crit­i­cal sec­tion of the Wikipedia entry. At least read that; I’ll wait:


The Unit­ed States Con­gress host­ed hear­ings on macro­eco­nom­ic mod­el­ing meth­ods on July 20, 2010, to inves­ti­gate why macro­econ­o­mists failed to fore­see the Finan­cial cri­sis of 2007–2010Robert Solow blast­ed DSGE mod­els cur­rent­ly in use:

I do not think that the cur­rent­ly pop­u­lar DSGE mod­els pass the smell test. They take it for grant­ed that the whole econ­o­my can be thought about as if it were a sin­gle, con­sis­tent per­son or dynasty car­ry­ing out a ratio­nal­ly designed, long-term plan, occa­sion­al­ly dis­turbed by unex­pect­ed shocks, but adapt­ing to them in a ratio­nal, con­sis­tent way… The pro­tag­o­nists of this idea make a claim to respectabil­i­ty by assert­ing that it is found­ed on what we know about micro­eco­nom­ic behav­ior, but I think that this claim is gen­er­al­ly pho­ny. The advo­cates no doubt believe what they say, but they seem to have stopped sniff­ing or to have lost their sense of smell alto­geth­er.’ (Solow’s state­ment to Con­gress, July 2010)

Now stop com­plain­ing about the mark: frankly, get­ting a fail for this essay is the least of your wor­ries. You seem to have alien­at­ed a large part of your peer group by this behaviour—who are you going to have lunch with after this per­for­mance? Butta­fuc­cin­who (yes, his nick­name sounds rude, but at present you’re in no posi­tion to accuse some­body else of rude­ness), for exam­ple, seems unlike­ly to ever want to play ball with you again:

I’m cer­tain­ly not in a posi­tion to deter­mine who’s right and wrong, and frankly don’t real­ly care, but did you even read Keen’s post? Two para­graphs below the part you excerpt­ed: “So econ­o­mists like Krugman—who describe them­selves as “New Keynesians”—have tweaked the base case to derive mod­els that “ape” real-world data, with “sticky” prices rather than per­fect­ly flex­i­ble ones, “fric­tions” that slow down quan­ti­ty adjust­ments, and imper­fect com­pe­ti­tion to gen­er­ate less-than-opti­mal social out­comes.”

Is there a four-let­ter word for some­one crit­i­cizes anoth­er per­son in a very pub­lic forum with­out read­ing what they’ve writ­ten? Or would a sev­en-let­ter word fit bet­ter? (Butta­fuc­cin­who)

No, that isn’t all. I believe your gang calls itself “New Key­ne­sian”, does­n’t it?

Well I am going to ban you from using that term in future: find anoth­er one.

Why? Well, for starters, the Post Key­ne­sian gang claims that you’re den­i­grat­ing their gang by claim­ing to be relat­ed to them, when you’re not. And I’ve done a bit of Tal­mu­dic research and found that they’re right: the SLIME mod­el you use—what? Oh, sor­ry, yes I meant IS-LM, my apologies—anyway, the IS-LM mod­el was­n’t devel­oped by Keynes at all.

Yes, I know you know it was devel­oped by Hicks, but it was­n’t as an inter­pre­ta­tion of Keynes—it was a “Wal­rasian” mod­el devel­oped before Hicks had read Keynes at all. Look, Hicks says so right here:

that mod­el was already in my mind before I wrote even the first of my papers on Keynes.’ (John Hicks, 1981, p. 140; empha­sis added)

And he also traces the mod­el to Wal­ras, not Keynes

the idea of the IS-LM dia­gram came to me as a result of the work I had been doing on three-way exchange, con­ceived in a Wal­rasian man­ner. I had already found a way of rep­re­sent­ing three-way exchange on a two-dimen­sion­al dia­gram (to appear in due course in chap­ter 5 of Val­ue and Cap­i­tal). As it appears there, it is a piece of sta­t­ics; but it was essen­tial to my approach (as already appears in “Wages and Inter­est: the Dynam­ic Prob­lem”) that sta­t­ic analy­sis of this sort could be car­ried over to “dynam­ics” by rede­f­i­n­i­tion of terms. So it was nat­ur­al for me to think that a sim­i­lar device could be used for the Keynes the­o­ry.’ (Hicks 1981, p. 141–142)

So at best,you’re a Hick­sian econ­o­mist. But actu­al­ly, even that won’t do, because Hicks dis­owned IS-LM in that same paper, on the basis that macro­eco­nom­ics can’t be mod­elled as an equi­lib­ri­um process:

I accord­ing­ly con­clude that the only way in which IS-LM analy­sis use­ful­ly survives—as any­thing more than a class­room gad­get, to be super­seded, lat­er on, by some­thing better—is in appli­ca­tion to a par­tic­u­lar kind of causal analy­sis, where the use of equi­lib­ri­um meth­ods, even a dras­tic use of equi­lib­ri­um meth­ods, is not inap­pro­pri­ate…

When one turns to ques­tions of pol­i­cy … the use of equi­lib­ri­um meth­ods is still more sus­pect. … There can be no change of pol­i­cy if every­thing is to go on as expected—if the econ­o­my is to remain in what (how­ev­er approx­i­mate­ly) may be regard­ed as its exist­ing equi­lib­ri­um. It may be hoped that, after the change in pol­i­cy, the econ­o­my will some­how, at some time in the future, set­tle into what may be regard­ed, in the same sense, as a new equi­lib­ri­um; but there must nec­es­sar­i­ly be a stage before that equi­lib­ri­um is reached. There must always be a prob­lem of tra­verse. For the study of a tra­verse, one has to have recourse to sequen­tial meth­ods of one kind or anoth­er.’ (Hicks 1981, p. 152–153)

So I think you could call your­self some­thing like “Old Hick­sians”; that would be OK. Or maybe “New Wal­rasians” when you do that DSGE thing.

Yes, I know you don’t like either of those names. But, to coin a phrase, “I Don’t Care”.


Hicks, John. 1981. “Is-Lm: An Expla­na­tion.” Jour­nal of Post Key­ne­sian Eco­nom­ics, 3(2), 139–54.

Solow, Robert M. 2003. “Dumb and Dumb­er in Macro­eco­nom­ics,” Festschrift for Joe Stiglitz. Colum­bia Uni­ver­si­ty:

____. 2001. “From Neo­clas­si­cal Growth The­o­ry to New Clas­si­cal Macro­eco­nom­ics,” J. H. Drèze, Advances in Macro­eco­nom­ic The­o­ry. New York: Pal­grave,

____. 2008. “The State of Macro­eco­nom­ics.” The Jour­nal of Eco­nom­ic Per­spec­tives, 22(1), 243–46.



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About Steve Keen

I am Professor of Economics and Head of Economics, History and Politics at Kingston University London, and a long time critic of conventional economic thought. As well as attacking mainstream thought in Debunking Economics, I am also developing an alternative dynamic approach to economic modelling. The key issue I am tackling here is the prospect for a debt-deflation on the back of the enormous private debts accumulated globally, and our very low rate of inflation.