The economic science blogosphere has a large give-and-take going on over Bob Lucas in addition to Tom Sargent's classic "Simon Wren-Lewis , Mark Thoma here and here and move dorsum through the links.
Influenza A virus subtype H5N1 few thoughts hither , every bit it bears on my WSJ oped from final calendar week in addition to my final post service on EFG in addition to how nosotros practise macro.
1. Views of Keynesian economics
Re-reading this newspaper , you lot volition survive struck nigh how much Lucas in addition to Sargent praise Keynesian models , which you'd think it is their role to destroy.
They called the Keynesian revolution a "remarkable intellectual event." they continued
Lucas in addition to Sargent brand a two-pronged declaration , i nigh theoretical coherence in addition to the other nigh the grand econometric failure of Keynesian models.
As I come across it , the master copy characteristic of "equilibrium" models Lucas in addition to Sargent inaugurated is that they set people , fourth dimension , in addition to economic science into macro.
Keynesian models model aggregates. Consumption depends on income. Investment depends on involvement rates. Labor render in addition to demand depend on wages. Money demand depends on income in addition to involvement rates. "Consumption" in addition to "investment" in addition to so forth are the fundamental objects to survive modeled.
"Equilibrium" models (using Lucas in addition to Sargent's word) model people in addition to technology. People brand simultaneous decisions across multiple goods , constrained yesteryear budget constraints -- if you lot swallow to a greater extent than in addition to relieve to a greater extent than , you lot must move to a greater extent than , or concur less money. Firms make decisions across multiple goods constrained yesteryear technology.
Putting people in addition to their simultaneous decisions dorsum to the catch of the model generates Lucas in addition to Sargent's master copy econometric conclusion -- Sims' "incredible" identifying restrictions. When people simultaneously create upward one's hear consumption , saving , labor render , in addition to so the variables describing each must fall over inward to the other. There is no argue for leaving (say) reward out of the consumption equation. But the entirely thing distinguishing i equation from only about other is which variables larn left out.
People brand decisions thinking nigh the future. I think "static" vs. "intertemporal" are goodness words to use. That observation goes dorsum to Friedman: consumption depends on permanent income , including expected hereafter income , non today's income. Decisions today are inevitably tied to expectations --rational or non -- nigh the future.
The lack of budget constraint (or the "missing equation" in addition to "Walras' law" issues much studied inward before Keynesian literature) strikes me every bit only about other large conceptual in addition to methodological deviation betwixt Keynesian models in addition to equilibrium models , which flows from putting people rather than aggregates at the catch of analysis.
Notice when you lot read whatsoever textbook that the microeconomic "demand" of a abrupt becomes the macroeconomic "plan." Why is that? Because demand curves honor budget constraints fifty-fifty at off-equilibrium prices. "Plans" similar consumption equals c bar summation alpha times income practise non honor whatsoever stated budget constraint. You're allowed to say you lot desire to swallow in addition to relieve to a greater extent than than income allows.
Optimization , rational expectations , in addition to flexible prices are the ballyhooed centerpieces of the start circular of equilibrium models to follow Lucas in addition to Sargent , such every bit Kydland in addition to Prescott's famous "time to build" model in addition to the subsequent "real delineate concern cycle" models (examples: Bob King in addition to Sergio Rebelo , John Long in addition to Charles Plosser). But I don't think these ingredients are primal to the program. The "new-Keynesian" (or , improve , DSGE) schoolhouse set inward pasty prices amongst all the other Lucas-Sargent ingredients , in addition to so nether the "equilibrium" banner. Mike Woodford's "Interest in addition to prices" is aimed proudly at that program. Sticky reward , distortions , in addition to so on are only every bit often included.
Simon Wren-Lewis questions whether Lucas in addition to Sargent were genuinely focusing on empirical failure or methodological critique. He suggested that accelerationist Phillips curves , though adapted after the failure in addition to so appearing a combat every bit epicycles , tin laissez passer the sack delineate concern human relationship for the data. (Lucas in addition to Sargent: "In economic science every bit inward other sciences ,...there is ever the promise that if a detail specific models fails i tin laissez passer the sack observe a to a greater extent than successful model based on roughly the same ideas.")
I think Simon is a combat likewise blasé nigh how tardily this modification is. Not entirely did inflation accelerate far faster than Keyensian models of the 1960s predicted , inflation dropped similar a rock inward 1982 , far faster than Keynesians thought possible based on adaptive expectations views. (If somebody tin laissez passer the sack observe the quote from Samuelson inward the early on 1980s predicting decades of depression to wring out inflation , delight add together to the comments.) Proud every bit only about self-identified Keynesians are nigh how good they think their unwritten , unquantified "model" fits the electrical current recession , deep unemployment amongst no motility inward inflation fits no Phillips flexure that was genuinely written before the crisis. Infinite wage stickiness is an ex-post innovation likewise , in addition to nonetheless only a verbal debating point.
But the newspaper is genuinely clear that empirical failure matters deeply to Lucas in addition to Sargent. They said that
Everyone was perfectly aware of the lack of "microfoundations" of Keynesian models , in addition to the 50 yr fruitless search for such foundations. But so long every bit the models worked , that had no existent behave on on their usage for the "scientific" in addition to technical policy advice Lucas in addition to Sargent so admired.
And rightly so. Chemistry , until the final few decades , lacked "microfoundations" inward quantum mechanics , start because nobody knew quantum mechanics , in addition to afterward because working out how chemicals react from start principles was likewise hard. That did non halt chemical scientific discipline from beingness a perfectly feasible science. Biology , until the final few decades , lacked "microfoundations" inward chemistry.
But chemical scientific discipline in addition to biological scientific discipline worked pretty well. Lucas in addition to Sargent pointed to , in addition to needed to indicate to , a grand empirical failure.
And that failure had to survive accompanied non only yesteryear "well , these are reasonable rules , but they're non microfounded." The failure had to survive accompanied yesteryear showing how the Keyensian model was logically flawed. That failure had to survive accompanied yesteryear a improve theory , which showed why the Keynesian equations were inconsistent amongst basic economics. That improve theory had already predicted Keynesian model's failure -- Friedman 1968 , Phelps , in addition to Lucas' prediction that the Phillips flexure would shift if exploited. That is a lot to a greater extent than than "methodological purity."
3. So what happened?
As I survey the landscape at nowadays , it is interesting how much of the macroeconomics Lucas in addition to Sargent praised has vanished. Quantitative , scientific discipline? Explicit statistical descriptions of economical behavior? Reliance of authorities officials on technical economical expertise? The usage of mathematical command theory to manage an economy? All that has vanished.
The sub-basements of primal banks own got large DSGE models , or combined models where you lot tin laissez passer the sack plow Lucas in addition to Sargent on in addition to off. But I think it's fair to say nobody takes the results real seriously. Policy -- our stimulus , for instance -- is based on dorsum of the envelope multipliers in addition to the ascendence in addition to expertise , if you're charitable , or the unvarnished , verbal , opinions if you're non , of management officials.
There are only about large-scale empirical DSGE models left inward academia too. But the vast mass of policy analysis does non usage them , every bit they did , say , the models of 1972. At conferences in addition to inward papers , academic move uses pocket-size scale toy models in addition to a lot of words. Models practise non seem to survive cumulative. Each newspaper adds a niggling twist ignoring all the previous niggling twists.
Influenza A virus subtype H5N1 consummate dissever occurred. "Equilibrium" models , inward which I include new-Keynesian DSGE models , took over academia. The policy the world stuck amongst uncomplicated ISLM logic -- non "models" inward the quantitative scientific tradition Lucas in addition to Sargent praised -- despite Lucas in addition to Sargent's devastating criticism. And , every bit I remarked inward the before spider web log posts , the "purely verbal" or literary trend of analysis is becoming to a greater extent than in addition to to a greater extent than mutual at nowadays inward academia every bit good every bit policy.
I'm non complaining nigh goodness vs. bad here. I write simpler in addition to simpler models every bit I grow older , in addition to pass to a greater extent than fourth dimension thinking in addition to writing nigh what those equations mean. It only is a fact nigh how nosotros practise things today in addition to the "scientific ," quantitative condition of macroeconomics.
Lucas in addition to Sargent's final sentence:
PS: Lucas in addition to Sargent own got a delicious quote nigh Keynesian's loss of organized faith inward their ain model , every bit applicable at nowadays every bit then:
Influenza A virus subtype H5N1 few thoughts hither , every bit it bears on my WSJ oped from final calendar week in addition to my final post service on EFG in addition to how nosotros practise macro.
1. Views of Keynesian economics
Re-reading this newspaper , you lot volition survive struck nigh how much Lucas in addition to Sargent praise Keynesian models , which you'd think it is their role to destroy.
They called the Keynesian revolution a "remarkable intellectual event." they continued
... only about of its [Keynesian Revolution] most of import features: the evolution of macroeconomics into a quantitative , scientific discipline , the evolution of explicit statistical descriptions of economical conduct , the increasing reliance of authorities officials on technical economical expertise , in addition to the introduction of the usage of mathematical command theory to manage an economy.
Keynesian theory evolved from a disconnected , qualitative speak nigh economical activeness into a arrangement of equations that tin laissez passer the sack survive compared to information inward a systematic way in addition to which provides an operational guide inward the necessarily quantitative undertaking of formulating monetary in addition to financial policy.
neither the success of the Keynesisan Revolution nor its eventual failure tin laissez passer the sack survive understood at the purely verbal grade at which Keynes himself wrote...
The Keynesian economic science they are praising hither is non Keynes' volume -- i of those large dingy things that people are nonetheless writing "what did Keynes genuinely mean" articles in addition to books nigh nearly a century afterward -- but the subsequent quantification effort: Hick's creation of the ISLM model , its elaboration into figurer models , estimation of those models , in addition to the usage of those models to brand quantitative forecasts of the effects of policy interventions.
"Quantitative , scientific discipline ," in addition to "technical economical expertise" agency nosotros analyze policies yesteryear existent models , non the opinions in addition to judgments of famous economists turned populace officials.
Yes , "mathematical command theory." Most readers volition survive likewise immature to recollect , but inward the early on 1970s academic journals were dynamic optimal command applied to simulations of large-scale Keynesian models.
Their destination was quite conservative: they wanted to save this neat achievement:
"Quantitative , scientific discipline ," in addition to "technical economical expertise" agency nosotros analyze policies yesteryear existent models , non the opinions in addition to judgments of famous economists turned populace officials.
Yes , "mathematical command theory." Most readers volition survive likewise immature to recollect , but inward the early on 1970s academic journals were dynamic optimal command applied to simulations of large-scale Keynesian models.
Their destination was quite conservative: they wanted to save this neat achievement:
The objectives of equilibrium delineate concern wheel theory are taken , without modification , from the destination which motivated the structure of the Keynesian macroeconometric models: to provide a scientifically based agency of assessing , quantitatively , the probable effects of choice economical policies.2. What was their basic criticism of Keynesian economics?
Lucas in addition to Sargent brand a two-pronged declaration , i nigh theoretical coherence in addition to the other nigh the grand econometric failure of Keynesian models.
As I come across it , the master copy characteristic of "equilibrium" models Lucas in addition to Sargent inaugurated is that they set people , fourth dimension , in addition to economic science into macro.
Keynesian models model aggregates. Consumption depends on income. Investment depends on involvement rates. Labor render in addition to demand depend on wages. Money demand depends on income in addition to involvement rates. "Consumption" in addition to "investment" in addition to so forth are the fundamental objects to survive modeled.
"Equilibrium" models (using Lucas in addition to Sargent's word) model people in addition to technology. People brand simultaneous decisions across multiple goods , constrained yesteryear budget constraints -- if you lot swallow to a greater extent than in addition to relieve to a greater extent than , you lot must move to a greater extent than , or concur less money. Firms make decisions across multiple goods constrained yesteryear technology.
Putting people in addition to their simultaneous decisions dorsum to the catch of the model generates Lucas in addition to Sargent's master copy econometric conclusion -- Sims' "incredible" identifying restrictions. When people simultaneously create upward one's hear consumption , saving , labor render , in addition to so the variables describing each must fall over inward to the other. There is no argue for leaving (say) reward out of the consumption equation. But the entirely thing distinguishing i equation from only about other is which variables larn left out.
People brand decisions thinking nigh the future. I think "static" vs. "intertemporal" are goodness words to use. That observation goes dorsum to Friedman: consumption depends on permanent income , including expected hereafter income , non today's income. Decisions today are inevitably tied to expectations --rational or non -- nigh the future.
Notice when you lot read whatsoever textbook that the microeconomic "demand" of a abrupt becomes the macroeconomic "plan." Why is that? Because demand curves honor budget constraints fifty-fifty at off-equilibrium prices. "Plans" similar consumption equals c bar summation alpha times income practise non honor whatsoever stated budget constraint. You're allowed to say you lot desire to swallow in addition to relieve to a greater extent than than income allows.
Optimization , rational expectations , in addition to flexible prices are the ballyhooed centerpieces of the start circular of equilibrium models to follow Lucas in addition to Sargent , such every bit Kydland in addition to Prescott's famous "time to build" model in addition to the subsequent "real delineate concern cycle" models (examples: Bob King in addition to Sergio Rebelo , John Long in addition to Charles Plosser). But I don't think these ingredients are primal to the program. The "new-Keynesian" (or , improve , DSGE) schoolhouse set inward pasty prices amongst all the other Lucas-Sargent ingredients , in addition to so nether the "equilibrium" banner. Mike Woodford's "Interest in addition to prices" is aimed proudly at that program. Sticky reward , distortions , in addition to so on are only every bit often included.
Simon Wren-Lewis questions whether Lucas in addition to Sargent were genuinely focusing on empirical failure or methodological critique. He suggested that accelerationist Phillips curves , though adapted after the failure in addition to so appearing a combat every bit epicycles , tin laissez passer the sack delineate concern human relationship for the data. (Lucas in addition to Sargent: "In economic science every bit inward other sciences ,...there is ever the promise that if a detail specific models fails i tin laissez passer the sack observe a to a greater extent than successful model based on roughly the same ideas.")
I think Simon is a combat likewise blasé nigh how tardily this modification is. Not entirely did inflation accelerate far faster than Keyensian models of the 1960s predicted , inflation dropped similar a rock inward 1982 , far faster than Keynesians thought possible based on adaptive expectations views. (If somebody tin laissez passer the sack observe the quote from Samuelson inward the early on 1980s predicting decades of depression to wring out inflation , delight add together to the comments.) Proud every bit only about self-identified Keynesians are nigh how good they think their unwritten , unquantified "model" fits the electrical current recession , deep unemployment amongst no motility inward inflation fits no Phillips flexure that was genuinely written before the crisis. Infinite wage stickiness is an ex-post innovation likewise , in addition to nonetheless only a verbal debating point.
But the newspaper is genuinely clear that empirical failure matters deeply to Lucas in addition to Sargent. They said that
Influenza A virus subtype H5N1 key chemical component inward all Keynesian models is a trade-off betwixt inflation in addition to existent output: the higher is the inflation charge per unit of measurement , the higher is output (or equivalently , the lower is the charge per unit of measurement of unemployment). For instance , the models of the tardily 1960s predicted a sustained U.S.A. of America unemployment charge per unit of measurement every bit consistent amongst a iv portion annual charge per unit of measurement of inflation. Based on this prediction , many economists at that fourth dimension urged a deliberate policy of inflation. [plus ça change...]... policy inward this menses should , according to all of these models , own got produced the lowest average unemployment rates for whatsoever decade since the 1940s. In fact , every bit nosotros know , they produced the highest unemployment rates since the 1930s. This was econometric failure on a grand scale. [My emphasis]Here every bit elsewhere , they said "econometric ," non economic. They meant it.
Everyone was perfectly aware of the lack of "microfoundations" of Keynesian models , in addition to the 50 yr fruitless search for such foundations. But so long every bit the models worked , that had no existent behave on on their usage for the "scientific" in addition to technical policy advice Lucas in addition to Sargent so admired.
And rightly so. Chemistry , until the final few decades , lacked "microfoundations" inward quantum mechanics , start because nobody knew quantum mechanics , in addition to afterward because working out how chemicals react from start principles was likewise hard. That did non halt chemical scientific discipline from beingness a perfectly feasible science. Biology , until the final few decades , lacked "microfoundations" inward chemistry.
But chemical scientific discipline in addition to biological scientific discipline worked pretty well. Lucas in addition to Sargent pointed to , in addition to needed to indicate to , a grand empirical failure.
And that failure had to survive accompanied non only yesteryear "well , these are reasonable rules , but they're non microfounded." The failure had to survive accompanied yesteryear showing how the Keyensian model was logically flawed. That failure had to survive accompanied yesteryear a improve theory , which showed why the Keynesian equations were inconsistent amongst basic economics. That improve theory had already predicted Keynesian model's failure -- Friedman 1968 , Phelps , in addition to Lucas' prediction that the Phillips flexure would shift if exploited. That is a lot to a greater extent than than "methodological purity."
3. So what happened?
As I survey the landscape at nowadays , it is interesting how much of the macroeconomics Lucas in addition to Sargent praised has vanished. Quantitative , scientific discipline? Explicit statistical descriptions of economical behavior? Reliance of authorities officials on technical economical expertise? The usage of mathematical command theory to manage an economy? All that has vanished.
The sub-basements of primal banks own got large DSGE models , or combined models where you lot tin laissez passer the sack plow Lucas in addition to Sargent on in addition to off. But I think it's fair to say nobody takes the results real seriously. Policy -- our stimulus , for instance -- is based on dorsum of the envelope multipliers in addition to the ascendence in addition to expertise , if you're charitable , or the unvarnished , verbal , opinions if you're non , of management officials.
There are only about large-scale empirical DSGE models left inward academia too. But the vast mass of policy analysis does non usage them , every bit they did , say , the models of 1972. At conferences in addition to inward papers , academic move uses pocket-size scale toy models in addition to a lot of words. Models practise non seem to survive cumulative. Each newspaper adds a niggling twist ignoring all the previous niggling twists.
Influenza A virus subtype H5N1 consummate dissever occurred. "Equilibrium" models , inward which I include new-Keynesian DSGE models , took over academia. The policy the world stuck amongst uncomplicated ISLM logic -- non "models" inward the quantitative scientific tradition Lucas in addition to Sargent praised -- despite Lucas in addition to Sargent's devastating criticism. And , every bit I remarked inward the before spider web log posts , the "purely verbal" or literary trend of analysis is becoming to a greater extent than in addition to to a greater extent than mutual at nowadays inward academia every bit good every bit policy.
I'm non complaining nigh goodness vs. bad here. I write simpler in addition to simpler models every bit I grow older , in addition to pass to a greater extent than fourth dimension thinking in addition to writing nigh what those equations mean. It only is a fact nigh how nosotros practise things today in addition to the "scientific ," quantitative condition of macroeconomics.
Lucas in addition to Sargent's final sentence:
Unless the at nowadays evident limits of these models are also frankly acknowledged in addition to radically dissimilar novel directions taken , the existent accomplishments of the Keynesian Revolution volition survive lost every bit sure enough every bit those nosotros know to survive illusory.Academic economic science took the start one-half to hart. Policy economic science froze inward place. But Lucas in addition to Sargent's "real accomplishments" were lost , or at to the lowest degree consciously abandoned , anyway.
PS: Lucas in addition to Sargent own got a delicious quote nigh Keynesian's loss of organized faith inward their ain model , every bit applicable at nowadays every bit then:
The electrical current moving ridge of protectionist sentiment directed at "saving jobs" would own got been answered 10 years agone amongst the Keynesian counterargument that financial policy tin laissez passer the sack accomplish the same terminate but to a greater extent than efficiently. Today , of class , no i would own got this response seriously , so it is non offered. Indeed , economists who 10 years agone championed Keynesian financial policy every bit an choice to inefficient straight off controls increasingly favor such controls every bit supplements to Keynesian policy.
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