Saturday, December 29, 2012

Quote of the Day: The Illusion of Stock-Picking Skill

Professional investors, including fund managers, fail a basic test of skill: persistent achievement. The diagnostic for the existence of any skills is the consistency of individual differences in achievement. The logic is simple: if any individual differences in any one year are entirely due to luck, the ranking of investors and funds will vary erratically and the year-to-year correlation will be zero. Where there is skill, however, the rankings will be more stable…

There is general agreement among researchers that nearly all stock pickers, whether they know it or not—and a few of them do—are playing a game of chance. The subjective experience of traders is that they are making sensible educated guesses in a situation of great uncertainty. In highly efficient markets, however, educated guesses are no more accurate than blind guesses.
This excerpt is from 2002 Nobel laureate psychologist and professor Daniel Kahneman in his insightful book Thinking, Fast and Slow p.214

Well Mr. Kahneman’s thesis seems to have been recently validated as passive long term investment funds (via equity bond index) has trumped active fund management represented by hedge funds 


The Economist notes,
The S&P 500 has now outperformed its hedge-fund rival for ten straight years, with the exception of 2008 when both fell sharply. A simple-minded investment portfolio—60% of it in shares and the rest in sovereign bonds—has delivered returns of more than 90% over the past decade, compared with a meagre 17% after fees for hedge funds...
The widening disparity means that randomness or providence or lady luck has increasingly played a bigger role in determining the performances of the fast expanding hedge fund industry. 

The same Economist article subliminally acknowledges this,
The average hedge fund is a lousy bet, and predicting which will thrive and which will disappoint is a task that would tax even a Nobel prizewinner.
Yet in the finance industry where many of the participants believe that they possess presumptuous knowledge which in reality exhibits inflated egos, the role played by luck/randomness exists in a vacuum. 

Why? As Mr. Kahneman from the same book p 216 explains,
The illusion of skill is not only an individual aberration; it is deeply ingrained in the culture of the industry. Facts that challenge such basic assumptions—and thereby threaten livelihoods and self esteem—are simply not absorbed. The mind does not digest them. This is particularly true of statistical studies  of performance, which provide base-rate information that people generally ignore when it clashes with their personal impressions from experience.

No comments: