Deductivism leading economists astray13 September, 2013 at 09:47 | Posted in Economics, Theory of Science & Methodology | 5 Comments
large bodies of social science are permeated by explanatory hubris. Economists and political scientists, in particular, rely on deductive models and statistical tools that are vastly less robust and reliable than their practitioners claim.
I can’t but concur. So let me just give you a couple of examples to validate this opinion.
In a recent interview Robert Lucas says he now believes that
the evidence on postwar recessions … overwhelmingly supports the dominant importance of real shocks.
So, according to Lucas, changes in tastes and technologies should be able to explain the main fluctuations in e.g. the unemployment that we have seen during the last six or seven decades. Let’s look at the facts and see if there is any strong evidence for this allegation. Just to take an example, here’s the situation in the eurozone:
What shocks to tastes and technologies drove the unemployment rate up and down like this in these countries? Not even a Nobel laureate could in his wildest imagination come up with any warranted and justified explanation solely based on changes in tastes and technologies.
Lucas is simply so wrong, so wrong, but how do we protect ourselves from this kind of scientific madness? Larry Summers has a suggestion well worth considering:
Modern scientific macroeconomics sees a (the?) crucial role of theory as the development of pseudo worlds or in Lucas’s (1980b) phrase the “provision of fully articulated, artificial economic systems that can serve as laboratories in which policies that would be prohibitively expensive to experiment with in actual economies can be tested out at much lower cost” and explicitly rejects the view that “theory is a collection of assertions about the actual economy” …
A great deal of the theoretical macroeconomics done by those professing to strive for rigor and generality, neither starts from empirical observation nor concludes with empirically verifiable prediction …
The typical approach is to write down a set of assumptions that seem in some sense reasonable, but are not subject to empirical test … and then derive their implications and report them as a conclusion. Since it is usually admitted that many considerations are omitted, the conclusion is rarely treated as a prediction …
However, an infinity of models can be created to justify any particular set of empirical predictions … What then do these exercises teach us about the world? … If empirical testing is ruled out, and persuasion is not attempted, in the end I am not sure these theoretical exercises teach us anything at all about the world we live in …
Reliance on deductive reasoning rather than theory based on empirical evidence is particularly pernicious when economists insist that the only meaningful questions are the ones their most recent models are designed to address. Serious economists who respond to questions about how today’s policies will affect tomorrow’s economy by taking refuge in technobabble about how the question is meaningless in a dynamic games context abdicate the field to those who are less timid. No small part of our current economic difficulties can be traced to ignorant zealots who gained influence by providing answers to questions that others labeled as meaningless or difficult. Sound theory based on evidence is surely our best protection against such quackery.
On the subject of deductivism, mentioned by both Elster and Summers, John Kay has a very interesting article showing how it has led economists to go astray in their – as my mentor Erik Dahmén used to say – “tool sheds”:
Consistency and rigour are features of a deductive approach, which draws conclusions from a group of axioms – and whose empirical relevance depends entirely on the universal validity of the axioms. The only descriptions that fully meet the requirements of consistency and rigour are completely artificial worlds, such as the “plug-and-play” environments of DSGE – or the Grand Theft Auto computer game.
For many people, deductive reasoning is the mark of science: induction – in which the argument is derived from the subject matter – is the characteristic method of history or literary criticism. But this is an artificial, exaggerated distinction. Scientific progress – not just in applied subjects such as engineering and medicine but also in more theoretical subjects including physics – is frequently the result of observation that something does work, which runs far ahead of any understanding of why it works.
Not within the economics profession. There, deductive reasoning based on logical inference from a specific set of a priori deductions is “exactly the right way to do things”. What is absurd is not the use of the deductive method but the claim to exclusivity made for it. This debate is not simply about mathematics versus poetry. Deductive reasoning necessarily draws on mathematics and formal logic: inductive reasoning, based on experience and above all careful observation, will often make use of statistics and mathematics.
Economics is not a technique in search of problems but a set of problems in need of solution. Such problems are varied and the solutions will inevitably be eclectic. Such pragmatic thinking requires not just deductive logic but an understanding of the processes of belief formation, of anthropology, psychology and organisational behaviour, and meticulous observation of what people, businesses and governments do.
The belief that models are not just useful tools but are capable of yielding comprehensive and universal descriptions of the world blinded proponents to realities that had been staring them in the face. That blindness made a big contribution to our present crisis, and conditions our confused responses to it. Economists – in government agencies as well as universities – were obsessively playing Grand Theft Auto while the world around them was falling apart.
The article is essential reading for all those who want to understand why mainstream – neoclassical – economists actively have contributed to causing todays’s economic crisis rather than to solving it.
Perhaps this becomes less perplexing to grasp when considering what one of its main proponents today – Robert Lucas – maintained already in 2003:
My thesis in this lecture is that macroeconomics in this original sense has succeeded: its central problem of depression-prevention has been solved, for all practical purposes, and has in fact been solved for many decades.
And this comes from an economist who has built his whole career on the assumption that people are hyper rational “robot imitations” with rational expectations and next to perfect ability to process information. Mirabile dictu!
So, yes, I can’t but concur with Elster — the deductivist modeling endeavour is leading economics astray.