Thursday, August 15, 2013

A Brief Defense of Economic Models

In this write up my goal is to convince some Austrians that mathematical models aren't as fallacious as they presume.  Before I get into my arguments I must first make this point and it is something that needs to be kept in mind as the readers works through this brief write up. Mathematics, insofar as it is utilized in economic theory, does not predict human action in a deterministic fashion, rather, it captures the laws of human action such that predictions can be made given the constraints of relevant conditions under examination within the theory.

To sum up the Austrian view of models, one could argue that they believe models use false assumptions and lead to fallacious results.  On the Austrian view, models cannot capture human action. I am not bold enough to claim that mathematical models can perfectly capture human action but I do think models are highly useful.  Consider the standard model of supply and demand.  It gives us proper results, is extremely intuitive and a wonderful teaching tool.  Austrians, on the other hand, believe that the assumed continuity of the supply and demand curves are false.  As far as I can tell, this is their primary objection to using this model. According to them, because supply and demand are not continuous it is much more unlikely to reach equilibrium.  I would just like to point out that adherents of this model do not assume that the supply and demand ever actually reach equilibrium, but rather, prices are always adjusting towards equilibrium.

But I digress.

If what Austrians said about mathematical models were true, I would not need to write this because I would probably agree with them.  However that is not the case.  Consider this quote out of one of the leading graduate school micro theory books:
"Imagine that you are trying to explain a particular phenomenon with one of two competing theories.  Neither fits the data perfectly, but the first does a somewhat better job according to the standard statistical measures.  At the same time, the theory is built on some hypotheses about behavior by individuals that are entirely ad hoc, whereas the second is based on a model of behavior that appeals to your intuition about how people act in this sort of situation.  I assert trying to decide which model does a better job of "explaining" is not simply a matter of looking at which fits better statistically.  The second model should gain credence because of its greater validity, which brings to bear, in an informal sense, other data" (Kreps, A Course in Microeconomic Theory, pg 8)
Does this quote seem to fit the Austrian argument that Chicago school economists are stat chasers and do not care about the validity of assumptions?  Quite the contrary actually.  It seems to me that Chicago School economists are concerned about human behavior/theory first and stats second.  I do not see why any economist should have a problem with this method of economics.  As long as the economist will admit some of the draw backs his assumptions might have, why should we completely throw models out the window? Note that when models are introduced through scholarly journals the author will always point out some of its downfalls but explain why it is still useful.

Another reason why I think models are important was touched on in my second paragraph.  Models are helpful learning tools because they are intuitive insights into real world phenomena.  Consider supply and demand again.  If I were to try and explain to someone why rent controls create housing shortages it is to my advantage to draw supply and demand curves and then show the different implications of keeping rent lower than the market clearing price.  It is much easier for the layman to see the consequences as a picture rather than sorting through all the material in their head.  Same goes for tariffs and minimum wage.  I have a hard time explaining why tariffs are bad even to a relatively knowledgeable audience, but as soon as I draw it out for them it clicks.

The last reason why I believe models are important is because even models that are falsified still help us gain knowledge.  This is because learning what assumptions lead to the false conclusions now gives us insight into why these assumptions won't work for future theories.  As long as the economist is trying to encompass human behavior as much as possible and it is fairly explanatory and predictive, why should anyone reject it? Models can have good explanatory power as to why things happen and to what will happen.

Lastly I would just like to point out this is barely scratching the surface of how much theory and thought goes into what makes a good economic model.  To simply reject these ideas based off of the use of models alone is preposterous

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