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Wednesday, July 29, 2015

'Using Math to Obfuscate — Observations from Finance

More from Paul Romer on "mathiness" -- this time the use of math in finance to obfuscate communication with regulators:

Using Math to Obfuscate — Observations from Finance: The usual narrative suggests that the new mathematical tools of modern finance were like the wings that Daedalus gave Icarus. The people who put these tools to work soared too high and crashed.
In two posts, here and here, Tim Johnson notes that two government investigations (one in the UK, the other in the US) tell a different tale. People in finance used math to hide what they were doing.
One of the premises I used to take for granted was that an argument presented using math would be more precise than the corresponding argument presented using words. Under this model, words from natural language are more flexible than math. They let us refer to concepts we do not yet fully understand. They are like rough prototypes. Then as our understanding grows, we use math to give words more precise definitions and meanings. ...
I assumed that because I was trying to use math to reason more precisely and to communicate more clearly, everyone would use it the same way. I knew that math, like words, could be used to confuse a reader, but I assumed that all of us who used math operated in a reputational equilibrium where obfuscating would be costly. I expected that in this equilibrium, we would see only the use of math to clarify and lend precision.
Unfortunately, I was wrong even about the equilibrium in the academic world, where mathiness is in fact used to obfuscate. In the world of for-profit finance, the return to obfuscation in communication with regulators is much higher, so there is every reason to expect that mathiness would be used liberally, particularly in mandated disclosures. ...
We should expect that there will be mistakes in math, just as there are mistakes in computer code. We should also expect some inaccuracies in the verbal claims about what the math says. A small number of errors of either type should not be a cause for alarm, particularly if the math is presented transparently so that readers can check the math itself and check whether it aligns with the words. In contrast, either opaque math or ambiguous verbal statements about the math should be grounds for suspicion. ...
Mathiness–exposition characterized by a systematic divergence between what the words say and what the math implies–should be rejected outright.

    Posted by on Wednesday, July 29, 2015 at 10:52 AM in Economics, Financial System, Methodology | Permalink  Comments (4)


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