Economics

What Economics Models Really Say

Why is there such an enormous gulf between what economists know and what they say in public?

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By Peter Turchin

A Review of Economics Rules: The Rights and Wrongs of the Dismal Science by Dani Rodrik (Norton, 2015)

The blurb on the jacket of Economics Rules says, “In this sharp, masterful book, Dani Rodrik, a leading critic from within, takes a close look at economics to examine when it falls short and when it works, to give a surprisingly upbeat account of the discipline.” I heartily agree with nearly all of this, with the exception of the “upbeat” part. As I will explain toward the end of this review, my view of economics, and, especially, of the role that economists play in public policy, is much more critical.

A central theme in the book is the role of mathematical models in economics. Formal models in economics and other social sciences are often disparaged. According to the critics (who include some economists, many other social scientists, and the overwhelming majority of historians), models oversimplify complex reality, employ unrealistic assumptions, and deny “agency” to human beings.

Rodrik rejects this critique. According to him, mathematical models— “simplifications designed to show how specific mechanisms work by isolating them from other, confounding effects”—are the true strength of economics. A simplified description of reality is not a shortcoming, it’s the essence of a good model.

My own training was in mathematical biology, and as a graduate student during the 1980s I saw the tail end of the “Math Wars” in ecology. By the 1990s the war was won, and any respectable department of ecology and evolution had to have on faculty at least one modeler. Today, the great majority of ecologists agree that a science cannot become a Science until and unless it develops a well-articulated body of mathematical theory.

In the social sciences, different disciplines made this transition at different times, with economics leading the pack and laggards, like history, undergoing this transition only now (hence cliodynamics—“history as science”; it’s worth noting that most American historians consider history not as a social science, but as one of the humanities).

I was, thus, a bit bemused to read Rodrik’s defense of mathematical models (haven’t economists resolved the Math Wars already?). But it’s an excellent defense—all aspiring cliodynamicists should read Economics Rules, if only for this reason.

The list of reasons why we need mathematical models in a scientific discipline is familiar to all who have extensive experience in modeling (and for those who don’t have such experience, I suggest you read Chapters 1 and 2 of Economics Rules). Models clarify the logic of hypotheses, ensure that predictions indeed follow from the premises, open our eyes to counterintuitive possibilities, suggest how predictions could be tested, and enable accumulation of knowledge. The advantage of clarity that mathematical models offer scientists is nicely illustrated in the following quote from Economics Rules: “We still have endless debates today about what Karl Marx, John Maynard Keynes, or Joseph Schumpeter really meant. … By contrast, no ink has ever been spilled over what Paul Samuelson, Joe Stiglitz, or Ken Arrow had in mind when they developed the theories that won them their Nobel.” The difference? The first three formulated their theories largely in verbal form, while the latter three developed mathematical models.

The value of the book, however, is in more than just weighing in on the usefulness of mathematical models. As Rodrik notes early in the book, “economics is by and large the only social science that remains almost entirely impenetrable to those who have not undertaken the requisite apprenticeship in graduate school.” And economics is “impenetrable” not because of mathematical models, at least not to someone trained in mathematical natural sciences (the math is universal), but because economists have developed an entirely distinct jargon that sets them apart from other disciplines and creates artificial barriers to understanding the many truly worthwhile insights from economics models.

Because I have not “undertaken the requisite apprenticeship”, I found very useful Rodrik’s explanations of the insights generated by such classic models in economics as the First Fundamental Theorem of Welfare Economics, the Principle of Comparative Advantage, and the General Theory of Second Best. Particularly illuminating were the discussion of what happens to the fundamental result of a model when we start systematically relaxing various assumptions on which it depends. This part of the book, together with the references that Rodrik provides, could serve as a basis for an excellent mini-course on what economics theory really tells us.

And a general take-home message that emerges from this discussion is that if we want to understand Big Questions—when do markets work or fail, what makes economies grow, and what are the effects of deficit spending—there is not one fundamental model, “the Model”. Instead, we need to study an array of models, each telling a partial story.

So far so good. But Rodrik, in my opinion, goes too far in denying the value of general theory. At one point he writes, “society does not have fundamental laws— at least, not quite in the same way that nature does.” And: “the same theory of evolution applies in both Northern and Southern Hemispheres,” but “economic models are different.”

Not really. Let’s take the theory of evolution. It’s not a single model. It’s a theoretical framework that includes hundreds, perhaps thousands of special case models, each telling only a partial story. To give an example, textbooks on evolutionary theory often start with a single-locus two-allele model (which gives us the famous Hardy-Weinberg Equilibrium). But you will need different models for haploid organisms (such as bacteria, who have a single unpaired chromosome), or for organisms reproducing asexually; and yet another set of models for phenotypic selection. Despite such diversity of modeling approaches, there is a theoretical unity in evolutionary biology. In particular, the conceptual framework of evolutionary theory provides a set of guidelines for the theoreticians on which model to use in which context.

And I don’t see how the situation is different in economics (and, more generally, social sciences). Yes, there is a multiplicity of models in economics, but you can’t just select one randomly (or worse, “cherry pick” among the results to suit your ideological agenda). There are rules for choosing appropriate models, and Rodrik devotes Chapter 3 of his book to explaining general principles of model selection in economics. In other words, theoretical frameworks are not simply compendia of models, they also include model selection rules (and a few other things).

Rodrik, thus, sells short the potential for general theory in social sciences. Naturally, economics, in particular, does not have such an elaborate, well-articulated, and empirically validated theoretical framework as evolutionary biology (and evolutionary biology, in turn, lags behind many subdisciplines of physics). But who is to say that economics will not develop to the same level in the future? We’ll see if we live long enough.

Let’s now shift gears and talk about Chapter 5, “When Economists Go Wrong.” To make the following discussion concrete, I will focus on a particular theoretical result in economics, the Principle of Comparative Advantage, and what this principle implies for trade policy. In popular press, of course, comparative advantage is always used as a justification for advocating free trade. Rodrik does an admirable job explaining why, under many conditions, free trade can lead to really negative consequences for economies and populations of countries that open themselves to international competition. For example, there is strategic behavior. A country may choose to protect its domestic industry with high tariffs and subsidize its exports in order to gain market share. Perhaps its leaders don’t understand the Principle of Comparative Advantage, not having the benefit of apprenticeship in economics. Or perhaps they care more about their country’s long-term survival in an anarchic international environment than about making immediate profit.

In one particularly revealing passage in the book, Rodrik writes,

consider how opening up trade—one of the key items of the Washington Consensus—was supposed to work. As barriers to imports were slashed, firms that were unable to compete internationally would shrink or close down, releasing their resources (workers, capital, managers) to be employed in other parts of the economy. More efficient, internationally competitive sectors, meanwhile, would expand, absorbing those resources and setting the stage for more rapid economic growth. In Latin American and African countries that adopted this strategy, the first part of this prediction largely materialized, but not the second. Manufacturing firms, previously protected by import barriers, took a big hit. But the expansion of new, export-oriented activities based on modern technologies lagged. Workers flooded less productive, informal service sectors such as petty trading instead. Overall productivity suffered. [italics are mine]

Washington Consensus outcomes in Latin America and Africa stand in sharp contrast with the experience of Asian countries. … Instead of liberalizing imports early on, South Korea, Taiwan, and later China all began their export push by directly subsidizing homegrown manufacturing. … All of them undertook industrial policies to nurture new manufacturing sectors and reduce their economies’ dependence on natural resources.

As Rodrik correctly stresses, these cases do not prove that standard economics is wrong. In short, “someone who advocates free trade because it will benefit everyone probably does not understand how comparative advantage really works.”

Models that were developed for “the way markets really work—or fail to work—in low-income settings with few firms, high barriers to entry, poor information, and malfunctioning institutions, these alternative models proved indispensable”—by telling us why countries that followed the Washington Consensus failed, and those who threw it to the wind succeeded.

But then how does one explain that nearly all economists—96 percent— strongly agree with the following statement: “Free trade improves the productive efficiency and offers consumers better choices, and in the long run these gains are much larger than any effects on unemployment” (Politicians Should Listen to Economists on Free Trade, by Bryan Riley, The Heritage Foundation, Feb.1, 2013; this was from a survey conducted by the University of Chicago’s Booth School of Business).

Rodrik argues that “the problem has to do more with the way economists present themselves in public than with the substance of the discipline.” “In public, the tendency is to close ranks and support free markets and free trade.”

But why is there such an enormous gulf between what economists know and what they say in public? One possible explanation is that policies, such as free trade, while often harming broad swaths of populations, tend to benefit narrow segments of economic elites. Perhaps the critics from the left (and a few “heterodox economists”) are right when they charge that economists speak what the powers-that-be want us to hear.

Whatever the explanation, I cannot agree that Rodrik’s book gives us “a surprisingly upbeat account of the discipline.” Economics may be a vibrant discipline, but most of the richness of its insights is hidden in academic publications behind the shield of specialist jargon, impenetrable to those who have not taken the requisite apprenticeship. And by closing ranks and unconditionally supporting free markets and free trade, economists have failed us, the general public. This is why we need more books like Economics Rules—so that we can find out what economics models really tell us.

Originally published at Cliodynamics: The Journal of Quantitative History and Cultural Evolution.


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  • Derryl Hermanutz

    In 1841 Friedrich List published his National System of Political Economy, describing how every nation that has developed its economy has done so via explicit national industrial policies that protect its nascent industries and internal markets with preferential tariffs and other barriers to “free trade”.

    As if to prove List’s point: less than 30 years later John A Macdonald — Canada’s first Prime Minister — enacted his “National Policies” to develop central Canadian banking, industry and commerce at the expense of US industrial competitors and the Maritime and Prairie “hinterlands” who were to be providers of resources and consumer markets for the manufactures.

    Free trade enriches industrially developed (capital intensive) “capitalist” regions and nations at the expense of resource-providing “worker” regions and nations. The “free trade benefits all” mantra is a propaganda slogan, not a historical observation; and not a logical implication of any empirically-informed theory that takes all relevant factors into account.

    “Models” explicity simplify reality in an effort to analytically examine the effects of individual factors. Real-world system are complex and dynamic. Changing one factor changes all the other factors in unpredictable ways. Reality cannot be “modeled”. But it can be “observed” and known empirically and historically.

    Patterns emerge and can be recognized. Patterns such as, “Mainstream economics serves as an intellectual priesthood whose job is to develop and defend narratives that morally justify the wealth, power and privilege of the owning and ruling class who make policies that serve their interest in acquiring and preserving their wealth, power and privilege.”

    Which is why an “authoritative consensus” develops around what John K Galbraith called “the conventional wisdom”. The conventional wisdom is usually visibly false. But to be accepted as an economic “authority” you have to preach it. Otherwise you are relegated to the hinterlands with the rest of the working class rubes.

    Insofar as economics is going to be about “reality”, you can’t take the “political” out of political economy.

    Models are made of “assumptions”. By tweaking the assumptions, you can make the models produce any outcome you choose. Mathematizing the models lends false precision to propaganda slogans. But it “works” as a morality narrative to convince the masses that the owning class “earned” and “deserve” their wealth, power and privileges.

    It’s like Einstein said about mathematized physics: Insofar as it is precise it is not about reality; and insofar as it is about reality it is not precise.

    • robertmkadar

      Always enjoy and learn a lot from your comments! Thank you.

    • Hanuman

      You are right on target for me! The certainty of math is used as a shroud. 2 + 2 = 4 is the most certain truth there can be. Philosophical necessity’s core is in mathematical truth and validity. But this is not science. Science grows and changes as new observations are made and new instruments are invented to make those new observations.

      Math departments and science departments hate each other. So do music departments and art departments, for that matter.

      Erik Reinert’s book, “How Rich Countries Got Rich and Why Poor Countries Stay Poor” is a book that completes the thoughts you just laid out for us.

      The math is there either as a tool to be used as such, or it is there to do as you say-justify crime.

      • Andrew

        I am not sure whether it is true that Maths departments and Science departments hate each other but there is a big difference between mathematical and scientific reasoning. The gold standard for Mathematical reasoning is internal consistency, the gold standard for scientific reasoning is rigorous experimental testing. Theories can be internally mathematically consistent but untrue. They can even be consistent with most observations but untrue because of anomalies (Newtonian physics). As for there being no doubt about what Paul Samuelson, Joe Stiglitz, or Ken Arrow had in mind, it is in the very nature of mathematics that it presents abstractions i,e, incomplete representations. Mathematics is a language and faces the same issues as any other form of language. It is just the fact that it is a language that only a small minority can use fluently that protects it from the myriad of criticisms, controversies and different perspectives that most statements in ordinary language are destined to face. You have to have a clear understanding of phenomena that can be expressed, defended and disputed in ordinary language before you can justifiably reduce it to a set of relationships expressed in mathematical terms. Used properly mathematics is a tool for presenting and communicating a process of reasoning and discovery not a tool to replace it.

        • Hanuman

          You’re right that hate is the wrong word. I guess I would say that there is sometimes friction between science and math departments as well as between music and art departments.

          Your last sentence is great! You say: “Used properly mathematics is a tool for presenting and communicating a process of reasoning and discovery not a tool to replace it.”

          Mainstream economics replaces experience with static ideas that work in theory but have no relation to the real world. Mathematical reasoning and models are fine, as long as they don’t replace real observation.

          As you know, math does not need the real world as a reference. It can exist (theoretically) alone, without a reality to contain it. The same cannot be true of science, and especially a social science.

          Lastly, the real problem is that all this intellectualization is like a drug. It is a distraction from the discussion all of us in America should be having. That discussion should be: What is political economy and why do all of us know nothing about it?

          Americans live in a bubble. For example, most people don’t know how things work, like toasters, cars, cell phones, etc., but they know that others know how they work. On top of that, people know that there are schools, universities, and degrees all devoted to knowing how things work.

          Yet when it comes to political economy, not only do people not understand it, they don’t even know the topic exists!

          It’s as if we are living in the 12th century and ascribe all events to the will of god. Even peasants in the 12th century had it better than us. They kept more of what they produced, did not deal with monopoly prices and thought control a la Edward Bernays.

          I think this is so much more important that discussing intellectual topics like mathematical models. The expertise that America thinks it has is really mostly about things that actually are petty and contrived. Intellectuality is really a display of manners that shows the world how cultured one is. This is the real function of knowledge in America.

          Economists who are part of this problem should be wearing white powdered wigs. Philosophy departments are a joke as well. What philosophy department teaches classical economists?

          Outside of the a few in the humanities that understand what I am saying, the humanities in America (and much of the developed world) are a joke. If you need some evidence, go to a web-page called the New Real Peer Review.

          It’s a twitter account that posts abstracts of academic papers in the humanities and social sciences reveal just how worthless these disciplines have become.

          https://twitter.com/realpeerreview?lang=en

          The most insulting thing of all, perhaps, is that liberals like the Democrats in America are called “The Left” by the media and by the clueless conservatives.

          Nowadays, the only people who consider themselves Marxists have Ph.D.’s. They are great in social situations where they are constantly networking and seeking a way to advertise their CV’s. Revolutionaries!

          There is no left in America. Intellectuality is not a substitute for real political economy and action. Talk is cheap.

        • Hanuman

          Andrew, I tried to respond to your reply but I used the edit button to correct a few typos. The good people at Evonomics are using a program that thinks editing is a sign of spam. Until they figure it out and free my comment I can only say you are right, hate is too strong a word.

          Math is not a substitute for life, just a tool to make ideas easier to use.

          • Andrew

            I received the text of your reply even though it did not publish. Thank you for that.

      • Patrick Cardiff

        Thanks for the citation. I will search up this book.

  • Nicholas Gruen

    Disappointing to see Peter Turchin fall for this scientistic line that formal mathematical knowledge somehow self-evidently trumps other kinds of knowledge. Formal mathematical models are a style of reasoning that has advantages and disadvantages. As I guess Turchin knows, there was a cliometrics craze (largely the US I think) in the 1950s and 60s based on similar notions. It didn’t get very far. Hayek is quite good on scientism, though himself is too biased against formal mathematical methods.

    Here’s Samuelson making a confession in 1986 about his own expectations of this kind of knowledge converging ever more closely towards fidelity to the world.

    “Let me make a confession. Back when I was 20 I could perceive the great progress that was being made in econometric methods. . . . I expected that the new econometrics would enable us to narrow down the uncertainties of our economic theories. . . . My confession is that this expectation has not worked out. . . . [I]t seems . . . that there does not accumulate a convergent body of econometric findings convergent on a testable truth.”

    • Patrick Cardiff

      This is astute. But are you not merely referring to GIGO?

      • Nicholas Gruen

        I can’t see why. Perhaps you’d care to elaborate?

    • Unknown Soldier

      I think Turchin is saying the opposite no? That there is over-reliance on mathematical models in economics. Quote: “I was, thus, a bit bemused to read Rodrik’s defense of mathematical models (haven’t economists resolved the Math Wars already?).”

      • Nicholas Gruen

        I think he’s saying there that he’s bemused about Rodrik’s NEED to defend mathematical models. He goes on to set out a whole bunch of reasons why it’s obvious formal models are better. Of course all those reasons are obvious. So why did Marx and Keynes and Schumpeter – I’d add Smith – not set out their arguments in formal models. Well Both Marx and Keynes did offer some formal structure to their work with equations etc, but they must have thought that for their purposes using formal models would be less effective than not. So since all the reasons for using formal models are obvious, and would have been obvious to all of those people – none of whom was totally ignorant of maths and some of whom were very proficient at it (like Keynes who, like Marshall was a ‘Wrangler’ at Cambridge) – they must have thought NOT using formal methods had its benefits in some circumstances. But we don’t get any curiosity from Turchin about what those advantages and those circumstances might be.

  • Macrocompassion

    I beg to differ. There are many partial models of our social system but unless they include the effects of it all, they will be unable to properly represent what is happening in their corner. A model of the whole social system is thought to be too big and complicated to understand but that is because of the amount of detail it apparently should contain. But there is an answer which avoids bot these kinds of problems and it is in my book about theoretical macroeconomics. The model is chosen to deliberately simplify what looks like a complex subject by not considering individuals, firms nor types pf manufacturing, but instead it looks at FUNCTIONS–what the various parts of the system actually do with respect to each other. It is attached below and has but 6 functioning entities to cover the whole of our social system. We need to look more generally at what otherwise is a complex subject. Kindly enlarge the model and then read SSRN 2865571 “Einstein’s Criterion Applied to Macroeconomics Modeling” in the open literature of the www.
    https://uploads.disquscdn.com/images/d4e1d967b89a591b0360a23e9fcf62ab7c85a7ee2371d923edc80a12f8126d81.jpg

  • Patrick Cardiff

    Right on! The more complex the system, the higher the likelihood for error, and breakdown. Even incomplete specifications will describe a biased aggregate; and bias grows when it’s integrated into the system – you get further away from a proper expected value. If you can’t include all the relevant variables you can’t rely on your number, you can’t interpret.

    Long term trade is a “big idea” that we observe ex post; we’re not “in control” of such outcomes. If you choose comparative advantage as an important variable, that is only one – economist-made factor (as the author makes clear) in a sea of policy potentials.

    No, we’re not supposed to “understand” a trade stance any more than we are to “explain” inequality, or find a correlation between “unemployment” and “inflation” or summarily make anything special about a J Curve.
    Since when have I personally been able to use information from a macro model, for anything.
    Economists should evaluate their discipline by measuring stuff in front of them.

  • Peter van den Engel

    I guess free trade became an ideal since the lack of it had created the Great Depression before WW2. You could say the ‘math’ of that proved the opposite should bring the solution/ without calculating it. It is a general understanding.
    That its succes also had everything to do with the opportunity at the time in many new consumer products to be developed, of course creates a general new opportunity in free trade/ that does not mean free trade is the best solution for all economic equations.

    Generaly markets inflate, so the oldest industries get to be the most expensive and then give opportunity to competitive markets in low wages, as we have seen in the textile and shoe industries. They are ‘exported’ and then imported again. The math evolves itself.

    However, when a young market in a country is less efficient than a competitor, it cannot compete with that/ and when it has no alternative eveloped sectors, obviously killing that through free trade does not help the internal labor market. So, indeed free trade is not a general medicine with always the same effect.
    I would say this does not depend on math/ but on logic.

    That governments can make a difference in developing new technology in their market, to compete with foreign; because otgerwise there industry would no thave earned the money; like China

    • Andrew

      I find Minsky’s account of what caused the great depression
      more plausible. As regards the role of international trade in economics I think
      that economics, history and politics often gets so mixed up that it is
      difficult to tell one from the other. Declining economic powers see
      international trade as the route back to greatness, but ignore the historical
      factors that serve far better to explain their former success and suggest that
      it can never return. The role of international trade also has a political
      aspect that tends to be veiled because it would embarrass our modern
      sensibilities but the idea that any nation can gain a persistent advantage and
      success through international competition contains implicit overtones of social
      Darwinism. All-in-all, all of the current economic prescriptions look plausible
      as abstractions but they all have practical limits in the real world and in
      relation to the expectations that are placed on them.

      I think Kate Raworth is right to suggest that we need a new
      economics that focuses on efficiency interpreted as getting more value out of
      what we have rather than on creating more. Under such a system we
      would depend less on trade and make better use of the resources closer to home.
      I think, with creativity, the scope for this is enormous and that it can
      constitute the next revolution in industry and the economy.

      • Peter van den Engel

        Thank you Adrew for your comment, I agree with you on some levels, and disagree on others, or to put it in less dualistic terms, I’m having ideas about it.

        You are right that Minsky’s model predicts the financial system to create a debt crisis and with it an economic crisis, as what happened in the Great Depression/ at the same time economists sat together in 1947; basicly ignoring it; and wrote neo libarism as a future economic model that involved free trade much more than the previous model had done/ although 70 years later Minsky again poved to be right, in the mean while economy had been very succesfull.

        You also note a difference, since the crisis in te previous century involved primarily companies; not so much private debt; and the last crises primarily debt in the financial industry itself, next to government debt, while companies did not have debt problems at all overall.
        I agree Minsky has a strong point/ but free trade made a big difference.

        As far as I know, (limited) free trade still is the status quo, so I don’t know what you are refering to, stating countries are trying to use it to uplift there economies, as if it did not exist. I can imagine it refers to GB, as an answer to brexit, although trade agreements are usually made in consensus.

        The alternative of creating a local ecological economy, refering to Kate Raworth; thanks for mentioning her, I had seen the donut and red about it before, now I subscribed to her blog; sure has interesting perspectives/ but I would not know why it should rule out free trade.
        During the popmusic fenomena, Europe imported most if it from England and the US, but at the same time also had local expressions if that, which done quite well as well. Although the international free trade was by far the biggest part. Where by the way Branson got his capital from, by evading import regulations.

  • Unknown Soldier

    This is quite disappointing in my opinion and shows exactly how economics are devoid of and in distance with philosophy and epistemology:

    “We still have endless debates today about what Karl Marx, John Maynard Keynes, or Joseph Schumpeter really meant. … By contrast, no ink has ever been spilled over what Paul Samuelson, Joe Stiglitz, or Ken Arrow had in mind when they developed the theories that won them their Nobel.”

    We know what they meant. Pretty well so. What we discuss is whether they were right or not. In Rodrik’s view, this can be done only using the specific approach he advocated (modelling etc). Also, quite a lot of ink has been shed on Samuelson, Arrow, Stiglitz’s and other similar theorists as well. However, they didn’t stir the same discussion for various reasons such as:
    1. They are recent
    2. They use a method “impenetrable to those who have not taken the requisite apprenticeship”, to use the writer’s expression. The efficient market hypothesis is a very elegant, simple and clear model. The problem is that it just doesn’t work. It does not describe the reality. Other economists have shown this using similar methods.
    3. They theorized BECAUSE Marx, Keynes or Schumpeter wrote their influential and world changing thesis.
    4. If you break down their axioms normatively and epistemologically you will get much more debate.

    In essence, what I think Rodrik means (and I make a personal projection here) is that there we should build opinions and world-views based on descriptive technocratic criteria. Not the other way around, have a normative view as a guideline, which you aim to attain by understanding the world around you. This is the main problem with this view. The post-modern rejection of “Big Narratives”. It is essentially an appeal-to-nature fallacy. The central fallacy of neoclassical and neoliberal approach to economics and society.

    My second take is this other quote here:

    /But Rodrik, in my opinion, goes too far in denying the value of general theory. At one point he writes, “society does not have fundamental laws— at least, not quite in the same way that nature does.” And: “the same theory of evolution applies in both Northern and Southern Hemispheres,” but “economic models are different.”/

    It’s like the first example that pops into mind when you talk of modelling is “The Theory of Evolution” or perhaps “The Big Bang”. I think both Rodrik and Turchin have a misunderstanding here.

    Rodrik correctly states that society does not have fundamental laws. But then uses an analogy with the theory of evolution to show that the mechanics are the same by build of nature, whereas economic models do not apply everywhere. Well, they do not apply because they are based on unsound and unrealistic axioms, which is exactly their perceived strength. their simplicity is also their weakness. I don’t think he denies any value of a Grand Unified Theory. he just doesn’t believe it exists, by the discipline’s own nature.

    Turchin then falls to the trap of commenting on the analogy to address the issue of using multiple models instead of a falsely perceived Grand Model of Evolution. Of course there are many specific models in biology too. The thing is that they explain and predict much more accurately than economic models do. they are probably more compatible with each other. The axioms there are provided by nature. So I think that Turchin doesn’t actually answer Rodrik’s point here.