Richard Bookstaber a long time finance practitioner/risk manager who has worked for Morgan Stanley, Salomon Brothers, Moore Capital and Bridgewater as well as the Financial Stability Oversight Council and the Office of Financial Research has written a broad-based attack on financial economics and the DSGE models now used by most central banks. Trust me he knows what he is writing about and in the interests of full disclosure I interacted with him when I worked at Salomon Brothers.
Although not cited he is writing in the tradition of Nicholas Nassim Taleb (“The Black Swan”) with his fundamental disagreement with the theoretical underpinnings of financial economics. Simply put in a world of radical uncertainty we don’t know the underlying probability distributions of future financial returns and we don’t even know the potential states of the world needed to calculate a probability distribution. He argues that modern finance theory is built around top down axioms based on deductive reasoning where an all knowing representative individual calculates the future probabilities for all of the known states of the world. And importantly the future probability distribution is based on historical evidence. Under radical uncertainty that simply does not work.
Instead he argues for agent based models built upon inductive reasoning where the actors are “reflexive” in the word used by George Soros, in that they respond to the actions of others. As much as economists envy physics, Bookstaber turns the Heisenberg uncertainty principle on them. Thus while financial theory works in normal times, in a crisis all bets are off as “stuff happens.”
What Bookstaber would like is to use agent based models that are used to model automobile traffic and schools of fish, for example, through the use of complexity theory. All this is fine and good, but aside from a narrative Bookstaber does not offer up a formal model for the financial markets. Perhaps he has one, but it is not here. Nevertheless he offers a road map for future research.
At times Bookstaber’s writing style is clear and lucid with analogies from literature motion pictures and military combat. He is a student of “OODA”, observe, orient, decide and act. He is particularly acute in his discussion of the origins of the financial crisis and is highly critical of the role played by Goldman Sachs in their failure to honor a small “novation” request from Bear Stearns, which brought that firm down. However, at other times his writing is dull and staid
Bookstaber has written an important book and it should be read by risk managers and policy officials. The old models failed in 2008, now almost ten years later it is time for new ones.
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