A provocative presentation entitled Conventional Wisdom and Pseudo-Science: Are we Blinded by Theory? took place in front of a sold out audience of 176 on June 19 at the Metropolitan Club. Rob Arnott, Chairman & CEO, Research Affiliates was the speaker who generously shared his unconventional thoughts in debunking several core theories of finance.
His objective was to take us on a whirlwind tour of areas where conventional wisdom can often lead one astray. The premise of Arnott’s talk is that much in the world of finance masquerades as science, but is not. When theory and data conflict the standard reflex is to dismiss the data.
In assuming that theory is correct, one must tacitly assume that all assumptions are correct. Unfortunately, assumptions are oftentimes incorrect, and is the cause of the fissures between theory and reality.
Almost every popular theory of finance can be debunked in some way based on a flaw in the assumptions required to make the theory work.
Efficient Markets, Miller-Modigliani, Modern Portfolio Theory, CAPM, Black Scholes, Cox-Ingersoll-Ross, Behavioral Finance, etc. –- they all can be taken down in an imperfect world where reality does not cooperate with the assumptions.
An easy example to refute the efficient market theory in the equity markets considers empirical data involving the Top Dog in a sector.
The Top Dog is ranked #1 by market capitalization in a sector, a market, a country, or the world.
To get to Top Dog status requires outperformance. Over the preceding 5 year period, the Top Dog in the US outperforms the broad market by 20%. A global Top Dog outperforms the average stock in the world market by an even more impressive 40% in the 5 years leading up to becoming the Top Dog.
Going forward one might expect equal performance by the Top Dog according to the Efficient Market theory. However, reality suggests underperformance. And not just a modest level of underperformance, data suggests the Top Dog underperforms the market vastly in the ensuing 5 year period. In fact, the entire gain that got them to Top Dog status is often given up as the Top Dogs generally deliver less than bonds and cash. Is this a peculiarity? Or simply evidence that markets are not as efficient as theory suggests?.
Arnott suggested that history could taken a different course. What if, instead of advancing efficient markets in 60’s, there was a promotion of deranged markets. The market is always missing and trying to mean revert? It would explain anomalies. What if a DAPM (disorderly asset pricing model) involving mean reversion was advanced? The Nobel Prize might have never been granted to William Sharpe for CAPM and his extension of Markowitz’s portfolio theory.
Refuting CAPM was an easy target as the theory assumes everyone on the planet can borrow or lend at the risk free rate while ignoring taxes and a host of other real factors. If all of the CAPM assumptions rang true, the theory proves you cannot beat a cap weighted market. Because the assumptions are not true, the conclusion of CAPM theory must be taken as only an approximation of fact.
Working backwards, the assumptions allow for the mathematics to work out. Do not make the mistake of believing the theory proves that is how the world ought to work. Rather, the theory is totally expected given the assumptions. When empirical gaps exist between data and theory, do not automatically assume the data is wrong or bend it in order to justify the theory. Just as important as knowing the theory is to perform a judicious search for gaps in the assumptions.
In summary, Arnott left the audience with a prudent message. Theories are wonderful, and it is not necessary to disregard theory. However, please do not confuse theory with fact. It is not.