Cliodynamics: The Journal of Quantitative History and Cultural Evolution

What Economics Models Really Say

A Review of Economics Rules: The Rights and Wrongs of the Dismal
Science by Dani Rodrik (Norton, 2015)
Peter Turchin
University of Connecticut
Seshat: Global History Databank

The blurb on the jacket of Economics Rules says, “In this sharp, masterful book, DaniRodrik, 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 thediscipline.” 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 humanbeings.
Rodrik rejects this critique. According to him, mathematical models—“simplifications designed to show how specific mechanisms work by isolating themfrom 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 ascience 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 thistransition only now (hence cliodynamics—“history as science”; it’s worth notingthat most American historians consider history not as a social science, but as oneof 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
Corresponding author’s e-mail: peter.turchin@uconn.edu
Citation: Turchin, Peter. 2017. What Economics Models Really Say. A review of Economics
Rules: The Rights and Wrongs of the Dismal Science by Dani Rodrik (Norton, 2015).
Cliodynamics 8: 80–84.

Turchin: Economic Models. Cliodynamics 8:1 (2017)
defense—all aspiring cliodynamicists should read Economics Rules, if only for thisreason.
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 whodon’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 thefollowing quote from Economics Rules: “We still have endless debates today about
what Karl Marx, John Maynard Keynes, or Joseph Schumpeter really meant. … Bycontrast, 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 theusefulness of mathematical models. As Rodrik notes early in the book, “economics
is by and large the only social science that remains almost entirely impenetrable tothose 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 apartfrom 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 ineconomics as the First Fundamental Theorem of Welfare Economics, the Principleof Comparative Advantage, and the General Theory of Second Best. Particularly
illuminating were the discussion of what happens to the fundamental result of amodel when we start systematically relaxing various assumptions on which itdepends. 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 reallytells 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 ofgeneral 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 of81

Turchin: Economic Models. Cliodynamics 8:1 (2017)
evolution applies in both Northern and Southern Hemispheres,” but “economicmodels are different.”
Not really. Let’s take the theory of evolution. It’s not a single model. It’s atheoretical framework that includes hundreds, perhaps thousands of special casemodels, 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 forphenotypic selection. Despite such diversity of modeling approaches, there is atheoretical unity in evolutionary biology. In particular, the conceptual frameworkof evolutionary theory provides a set of guidelines for the theoreticians on whichmodel 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 yourideological agenda). There are rules for choosing appropriate models, and Rodrik
devotes Chapter 3 of his book to explaining general principles of model selectionin economics. In other words, theoretical frameworks are not simply compendia ofmodels, 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, wellarticulated, and empirically validated theoretical framework as evolutionary
biology (and evolutionary biology, in turn, lags behind many subdisciplines ofphysics). But who is to say that economics will not develop to the same level in thefuture? 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 theoreticalresult in economics, the Principle of Comparative Advantage, and what thisprinciple implies for trade policy. In popular press, of course, comparativeadvantage is always used as a justification for advocating free trade. Rodrik does
an admirable job explaining why, under many conditions, free trade can lead toreally 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 ofapprenticeship 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,82

Turchin: Economic Models. Cliodynamics 8:1 (2017)consider how opening up trade—one of the key items of theWashington Consensus—was supposed to work. As barriers toimports were slashed, firms that were unable to competeinternationally would shrink or close down, releasing their resources(workers, capital, managers) to be employed in other parts of theeconomy. More efficient, internationally competitive sectors,meanwhile, would expand, absorbing those resources and setting thestage for more rapid economic growth. In Latin American and Africancountries 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 theexpansion 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 standin sharp contrast with the experience of Asian countries. … Instead ofliberalizing 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 iswrong. In short, “someone who advocates free trade because it will benefit
everyone probably does not understand how comparative advantage reallyworks.”
Models that were developed for “the way markets really work—or fail towork—in low-income settings with few firms, high barriers to entry, poor
information, and malfunctioning institutions, these alternative models provedindispensable”—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 aremuch larger than any effects on unemployment” (Politicians Should Listen toEconomists 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 ofBusiness).
83Turchin: Economic Models. Cliodynamics 8:1 (2017)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 andwhat they say in public? One possible explanation is that policies, such as freetrade, 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 powersthat-be want us to hear.
Whatever the explanation, I cannot agree that Rodrik’s book gives us “asurprisingly upbeat account of the discipline.” Economics may be a vibrantdiscipline, 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.

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