Home > Uncategorized > What is Post Keynesian Economics?

What is Post Keynesian Economics?

from Lars Syll

encycJohn Maynard Keynes’s 1936 book The General Theory of Employment, Interest, and Money attempted to overthrow classical theory and revolutionize how economists think about the economy. Economists who build upon Keynes’s General Theory to analyze the economic problems of the twenty-first-century global economy are called Post Keynesians. Keynes’s “principle of effective demand” (1936, chap. 2) declared that the axioms underlying classical theory were not applicable to a money-using, entrepreneurial economic system. Consequently, the mainstream theory’s “teaching is misleading and disastrous if we attempt to apply it to the facts of experience” (Keynes 1936, p. 3). To develop an economic theory applicable to a monetary economy, Keynes suggested rejecting three basic axioms of classical economics (1936, p. 16).

Unfortunately, the axioms that Keynes suggested for rejection are still part of the foundation of twenty-first-century mainstream economic theory. Post Keynesians have thrown out the three axioms that Keynes suggested rejecting in The General Theory. The rejected axioms are the ergodic axiom, the gross-substitution axiom, and the neutral-money axiom … Only if these axioms are rejected can a model be developed that has the following characteristics:

•Money matters in the long and short run, that is, changes in the money supply can affect decisions that determine the level of employment and real economic output.

•As the economic system moves from an irrevocable past to an uncertain future, decision makers recognize that they make important, costly decisions in uncertain conditions where reliable, rational calculations regarding the future are impossible.

•People and organizations enter into monetary contracts. These money contracts are a human institution developed to efficiently organize time-consuming production and exchange processes. The money-wage contract is the most ubiquitous of these contracts.

•Unemployment, rather than full employment, is a common laissez-faire situation in a market-oriented, monetary production economy.

•The ergodic axiom postulates that all future events are actuarially certain, that is, that the future can be accurately forecasted from an analysis of existing market data. Consequently, this axiom implies that income earned at any employment level is entirely spent either on produced goods for today’s consumption or on buying investment goods that will be used to produce goods for the (known) future consumption of today’s savers. In other words, orthodox theory assumes that all income is always immediately spent on producibles, so there is never a lack of effective demand for things that industry can produce at full employment … Post Keynesian theory rejects the ergodic axiom.

In Post Keynesian theory … people recognize that the future is uncertain (nonergodic) and cannot be reliably predicted.

Paul Davidson

The financial crisis of 2007-08 hit most laymen and economists with surprise. What was it that went wrong with our macroeconomic models, since they obviously did not foresee the collapse or even made it conceivable?  

There are many who have ventured to answer that question. And they have come up with a variety of answers, ranging from the exaggerated mathematization of economics, to irrational and corrupt politicians.

0But the root of our problem goes much deeper. It ultimately goes back to how we look upon the data we are handling. In ‘modern’ macroeconomics — Dynamic Stochastic General Equilibrium, New Synthesis, New Classical and New ‘Keynesian’ — variables are treated as if drawn from a known “data-generating process” that unfolds over time and on which we therefore have access to heaps of historical time-series. If we do not assume that we know the ‘data-generating process’ – if we do not have the ‘true’ model – the whole edifice collapses. And of course it has to. I mean, who honestly believes that we should have access to this mythical Holy Grail, the data-generating process?

‘Modern’ macroeconomics obviously did not anticipate the enormity of the problems that unregulated ‘efficient’ financial markets created. Why? Because it builds on the myth of us knowing the ‘data-generating process’ and that we can describe the variables of our evolving economies as drawn from an urn containing stochastic probability functions with known means and variances.

4273570080_b188a92980This is like saying that you are going on a holiday-trip and that you know that the chance the weather being sunny is at least 30%, and that this is enough for you to decide on bringing along your sunglasses or not. You are supposed to be able to calculate the expected utility based on the given probability of sunny weather and make a simple decision of either-or. Uncertainty is reduced to risk.

But as Keynes convincingly argued in his monumental Treatise on Probability (1921), this is not always possible. Often we simply do not know. According to one model the chance of sunny weather is perhaps somewhere around 10% and according to another – equally good – model the chance is perhaps somewhere around 40%. We cannot put exact numbers on these assessments. We cannot calculate means and variances. There are no given probability distributions that we can appeal to.

In the end this is what it all boils down to. We all know that many activities, relations, processes and events are of the Keynesian uncertainty-type. The data do not unequivocally single out one decision as the only ‘rational’ one. Neither the economist, nor the deciding individual, can fully pre-specify how people will decide when facing uncertainties and ambiguities that are ontological facts of the way the world works.

wrongrightSome macroeconomists, however, still want to be able to use their hammer. So they decide to pretend that the world looks like a nail, and pretend that uncertainty can be reduced to risk. So they construct their mathematical models on that assumption. The result: financial crises and economic havoc.

How much better – how much bigger chance that we do not lull us into the comforting thought that we know everything and that everything is measurable and we have everything under control – if instead we could just admit that we often simply do not know, and that we have to live with that uncertainty as well as it goes.

Fooling people into believing that one can cope with an unknown economic future in a way similar to playing at the roulette wheels, is a sure recipe for only one thing — economic disaster.

  1. Risk Analyst
    June 1, 2017 at 7:58 pm

    As to characteristic #1 on the impact of money supply changes, this was definitely true for Keynes and when Davidson originally wrote this, but I’m not sure it is accurate now. Quantitative easing especially by the Fed in the last recession fundamentally changed the relationships between excess reserves, money, interest rates and spending. The Fed’s interest rate targeting supports an endogenous money supply argument. Money supply changes do not “affect decisions,” but rather decisions affect the money supply. Even if a consumer has only $10 cash in his wallet, he can still buy $5,000 with his credit card. If Julie Investor sees her ETF fund go up $5,000 she bases her purchase on that and not what her money wage was last week. The technology changed and the idea of a money supply needs to be updated to one of credit/debt.

  2. dmf
    June 1, 2017 at 11:06 pm
  3. Charles
    June 2, 2017 at 12:11 pm

    I have a question: Does anyone believe the debt selling spree of the FED prior to the ’08 collapse had anything to do with the collapse?

    • June 7, 2017 at 4:24 am

      Do you have data on this debt selling spree?

  4. June 5, 2017 at 3:55 pm

    I’ve made this comment on the “10 best books” blog:

    “Read with great interest the Sekera paper on public goods.
    Good list of categories of goods and services to be included.

    Unfortunately, as done by all economists, only those categories are included
    that do not threaten the very basics of economics.

    Why trade balance is not included?”

    Nobody answered. Sekera didn’t too.
    May I ask again anybody to satisfy my curiosity?

  5. Norman L. Roth
    June 6, 2017 at 10:37 pm

    June 06 2017

    Very clearly explained M. Syll ! Very much in the spirit of Gunnar Myrdal’s classic demolition of General Equilibrium in 1957, albeit in a somewhat different {but not unrelated } context. Speaking of “Disaster..at the Roulette wheels”, didn’t Keynes himself, when he was administering Cambridge’s Investment portfolio, ALMOST, go to the brink with his own miscalculation on the relationship between risk and uncertainty ? I would normally check out Skidelsky’s account of this event, which made Keynes quite ill. But I’m sure Paul Davidson could do it right-off the top of his memory bank. I like your {quasi}-Venn diagram of the relationship between RISK and UNCERTAINTY. Sort of reminds me of my Venn illustrations
    of the Current Conception of the Standard of Life in Chapter 2 of TELOS & TECHNOS.
    I would have gone for an overlap in your diagram, above. But you must have a good reason for doing it the way you did. As you may recall, Keynes thought that when confronted with authentic uncertainty situations, which could not be reduced to RISK models via the “calculus of probability”, most Decision makers followed one of two directions. They either pretended there was an underlying “ergodicism” and did what they had done in the past: Or they observed what their peers were doing and followed the herd more or less. .I know the dilemma from my own experience. It does not make for sound sleeping patterns.

    GOOGLE:Norman L. Roth

  6. Yoshinori Shiozawa
    August 4, 2019 at 11:17 am

    I do not know why this post becomes among Top Posts- last 48 hours as of August 2, 2019. Main post is dated December 12, 2013. The last comment is dated November 10, 2016 at 2:07. It is good to reflect on the problems posed many years ago.

    I am rather happy to find this old post, because I have just posted a complaint on his blog series that it would be better for him to talk more on heterodox economics. Post Keynesian economics is one of it.
    See my fifth comment (dated August 2, 2019) to the page

    If I have to classify myself, I an a Post Keynesian of a Sraffian strand, but these names are not important, because opinions are very different among those who shares the same name of school and strand.

    This post is uploaded by Lars Syll but the text is by Paul Davidson. There are no comments of Lars Syll. I wonder why Syll chose to post this part of Davidson text. Does he totally agree with Davidson? Or, does he have some points of doubt or objection? I do not know.

    From my own point of view, this text by Paul Davison includes a grave flaw that became more clear from six years of Abenomics. This economic policy bundle of Prime Minister Abe of Japan is principally based on the contentions of “reflation” group which is inspired by Paul Krugman’s paper: It’s baaack: Japan’s Slump and the return of Liquidity Trap (Brookings Papers on Economic Activity, 2:1998. See also the paper by Krugman “It’s Baaack, Twenty Years Later”).

    Click to access 1998b_bpea_krugman_dominquez_rogoff.pdf

    Click to access Its-baaack.pdf

    I do not argue Krugman. I want to point one proposition of Paul Davidson’s seems to be proved to be wrong by facts.

    At the top of the several pillars that he considers basis of a new system, Davidson wrote:
    “Money matters in the long and short run, that is, changes in the money supply can affect decisions that determine the level of employment and real economic output.”

    The first arrow of Abenomics (there were three arrows in the original Abenomics) is to increase monetary basis and money stock by a financial easing of “different dimension” according to Mr. Kuroda, the Governor of Bank of Japan (BOJ). As intended by Mr. Kuroda, the monetary base was increased enormously, but the increase mainly occurred to the current accounts at the BOJ. That part did not flew out from BOJ and money stock did not increased as it was expected. Details omitting, Mr. Kuroda could not realize his original policy commitment that he will raise the inflations rate up to 2 % within 2 years. Six years have passed and he could not even realize his target of 2 % inflation.

    Now come back to Davison’s first pillar. Did changes in the money supply affect decisions (of entrepreneurs and consumers) and increased the level of employment and real economic output? The answer is quite negative.

    As for the unemployment, the rate of unemployment decreased much. But many people point that this is rather a result of aging of Japan (Active population started to decrease since 1995 and total population started to decrease since 2008). The total output (measured in real and nominal GDP) is still stagnating.

    The economic theory that was at the back of the First Arrow of Abenomics was much inspired by quantity theory of money. I wonder why Davidson admitted the similar proposition as one of pillars of his system.

    The main proposal to Lars Syll in my comment to his post “Arrow-Debreu and the Bourbaki illusion of rigour” was the suggestion that he may better contribute to economics when he points possible errors of heterodox economics.


    He could have pointed this flaw in Davidson’s economics, but he missed the chance. Of course, I admit, it was not as easy as now to do it.
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