15/10/17: Concentration Risk & Beyond: Markets & Winners

An excellent summary of several key concepts in investment worth reading: "So Few Market Winners, So Much Dead Weight" by Barry Ritholtz of Bloomberg View.  Based on an earlier NY Times article that itself profiles new research by Hendrik Bessembinder from Arizona State University, Ritholtz notes that:

• "Only 4 percent of all publicly traded stocks account for all of the net wealth earned by investors in the stock market since 1926, he has found. A mere 30 stocks account for 30 percent of the net wealth generated by stocks in that long period, and 50 stocks account for 40 percent of the net wealth. Let that sink in a moment: Only one in 25 companies are responsible for all stock market gains. The other 24 of 25 stocks -- that’s 96 percent -- are essentially worthless ballast."

Which brings us to the key concepts related to this observation:

1. Concentration risk: This an obvious one. In today's markets, returns are exceptionally concentrated within just a handful of stocks. Which puts the argument in favour of diversification through a test. Traditionally, we think of diversification as a long-term protection against risks of markets decline. But it can also be seen as coming at a cost of foregone returns. Think of holding 96 stocks that have zero returns against four stocks that yield high returns, and at the same time weighing these holdings in return-neutral fashion, e.g. by their market capitalization.  
2. Strategic approaches to capturing growth drivers in your portfolio: There are, as Ritholtz notes, two: exclusivity (active winners picking) and exclusivity (passive market indexing). Which also rounds off to diversification. 
3. Behavioral drivers matter: Behavioral biases can wreck havoc with both selecting and holding 'winners-geared' portfolios (as noted by Rithholtz's discussion of exclusivity approach). But inclusivity  or indexing is also biases -prone, although Ritholtz does not dig deeper into that. In reality, the two approaches are almost symmetric in behavioral biases impacts. Worse, as proliferation of index-based ETFs marches on, the two approaches to investment are becoming practically indistinguishable. In pursuit of alpha, investors are increasingly being caught in chasing more specialist ETFs (index-based funds), just as they were before caught in a pursuit of more concentrated holdings of individual 'winners' shares.
4. Statistically, markets are neither homoscedastic nor Gaussian: In most cases, there are deeper layers of statistical meaning to returns than simple "Book Profit" or "Stop-loss" heuristics can support. Which is not just a behavioral constraint, but a more fundamental point about visibility of investment returns. As Ritholtz correctly notes, long-term absolute winners do change. But that change is not gradual, even if time horizons for it can be glacial. 

All of these points is something we cover in our Investment Theory class and Applied Investment and Trading course, and some parts we also touch upon in the Risk and Resilience course. Point 4 relates to what we do, briefly, discuss in Business Statistics class. So it is quite nice to have all of these important issues touched upon in a single article.

14/2/2014: Buffett's Alpha Demystified... or not?

Warren Buffett is probably the most legendary of all investors and his Berkshire Hathaway, despite numerous statements by Buffett explaining his investment philosophy, is still shrouded in a veil of mystery and magic.

The more you wonder about Buffett's fantastic historical track record, the more you ask whether the returns he amassed are a matter of luck, skill, unique strategy or all of the above.

"Buffett’s Alpha" by Andrea Frazzini, David Kabiller, and Lasse H. Pedersen (NBER Working Paper 19681 http://www.nber.org/papers/w19681, November 2013) shows that "looking at all U.S. stocks from 1926 to 2011 that have been traded for more than 30 years, …Berkshire Hathaway has the highest Sharpe ratio among all. Similarly, Buffett has a higher Sharpe ratio than all U.S. mutual funds that have been around for more than 30 years." In fact, for the period 1976-2011, Berkshire Hathaway realized Sharpe ratio stands at impressive 0.76, and "Berkshire has a significant alpha to traditional risk factors." According to the authors, "adjusting for the market exposure, Buffett’s information ratio is even lower, 0.66. This Sharpe ratio reflects high average returns, but also significant risk and periods of losses and significant drawdowns."

According to authors, this begs a question: "If his Sharpe ratio is very good but not super-human, then how did Buffett become among the richest in the world?"

The study looks at Buffett's performance and finds that "The answer is that Buffett has boosted his returns by using leverage, and that he has stuck to a good strategy for a very long time period, surviving rough periods where others might have been forced into a fire sale or a career shift. We estimate that Buffett applies a leverage of about 1.6-to-1, boosting both his risk and excess return in that proportion."

The conclusion is that "his many accomplishments include having the conviction, wherewithal, and skill to operate with leverage and significant risk over a number of decades."


But the above still leaves open a key question: "How does Buffett pick stocks to achieve this attractive return stream that can be leveraged?"

The authors "…identify several general features of his portfolio: He buys stocks that are
-- “safe” (with low beta and low volatility),
-- “cheap” (i.e., value stocks with low price-to-book ratios), and
-- high-quality (meaning stocks that profitable, stable, growing, and with high payout ratios).
This statistical finding is certainly consistent with Graham and Dodd (1934) and Buffett’s writings, e.g.: "Whether we’re talking about socks or stocks, I like buying quality merchandise when it is marked down"  – Warren Buffett, Berkshire Hathaway Inc., Annual Report, 2008."


Of course, such a strategy is not novel and Ben Graham's original factors for selection are very much in line with it, let alone more sophisticated screening factors. Everyone knows (whether they act on this knowledge or not is a different matter altogether) that low risk, cheap, and high quality stocks "tend to perform well in general, not just the ones that Buffett buys. Hence, perhaps these characteristics can explain Buffett’s investment? Or, is his performance driven by an idiosyncratic Buffett skill that cannot be quantified?"

The authors look at these questions as well. "The standard academic factors that capture the market, size, value, and momentum premia cannot explain Buffett’s performance so his success has to date been a mystery (Martin and Puthenpurackal (2008)). Given Buffett’s tendency to buy stocks with low return risk and low fundamental risk, we further adjust his performance for the Betting-Against-Beta (BAB) factor of Frazzini and Pedersen (2013) and the Quality Minus Junk (QMJ) factor of Asness, Frazzini, and Pedersen (2013)."

And then 'Eureka!': "We find that accounting for these factors explains a large part of Buffett's performance. In other words, accounting for the general tendency of high-quality, safe, and cheap stocks to outperform can explain much of Buffett’s performance and controlling for these factors makes Buffett’s alpha statistically insignificant… Buffett’s genius thus appears to be at least partly in recognizing early on, implicitly or explicitly, that these factors work, applying leverage without ever having to fire sale, and sticking to his principles. Perhaps this is what he means by his modest comment: "Ben Graham taught me 45 years ago that in investing it is not necessary to do extraordinary things to get extraordinary results." – Warren Buffett, Berkshire Hathaway Inc., Annual Report, 1994."


There is more to be asked about Warren Buffett's investment style and strategy. "…we consider whether Buffett’s skill is due to his ability to buy the right stocks versus his ability as a CEO. Said differently, is Buffett mainly an investor or a manager?"

Authors oblige: "To address this, we decompose Berkshire’s returns into a part due to investments in publicly traded stocks and another part due to private companies run within Berkshire. The idea is that the return of the public stocks is mainly driven by Buffett’s stock selection skill, whereas the private companies could also have a larger element of management."

Another 'Eureka!' moment beckons: "We find that both public and private companies contribute to Buffett’s performance, but the portfolio of public stocks performs the best, suggesting that Buffett’s skill is mostly in stock selection. Why then does Buffett rely heavily on private companies as well, including insurance and reinsurance businesses? One reason might be that this structure provides a steady source of financing, allowing him to leverage his stock selection ability. Indeed, we find that 36% of Buffett’s liabilities consist of insurance float with an average cost below the T-Bill rate.


So core conclusions on Buffett's genius: "In summary, we find that Buffett has developed a unique access to leverage that he has invested in safe, high-quality, cheap stocks and that these key characteristics can largely explain his impressive performance. Buffett’s unique access to leverage is consistent with the idea that he can earn BAB returns driven by other investors’ leverage constraints. Further, both value and quality predict returns and both are needed to explain Buffett’s performance. Buffett’s performance appears not to be luck, but an expression that value and quality investing can be implemented in an actual portfolio (although, of course, not by all investors who must collectively hold the market)."

Awesome study!