Big Ideas

Are financial markets best viewed as massively multiplayer gambling? In his March 2017 paper entitled “Why Markets Are Inefficient: A Gambling ‘Theory’ of Financial Markets for Practitioners and Theorists”, Steven Moffitt presents a model of financial markets based on the perspective of an analytical/enlightened gambler. The gambler believes that: (1) actions of many players (some astute, some mediocre and some fools) drive prices; and, (2) markets adapt such that all static trading systems eventually fail. The gambler combines fundamental laws of gambling, knowledge of trading strategies of other market participants and data analysis to identify and exploit trading opportunities. The gambler translates this general strategy into a specific plan that algorithmically generate trades. Key aspects of the model are, as proposed: Keep Reading

Do narratives (stories) sometimes trump rationality in financial markets? In his January 2017 paper entitled “Narrative Economics”, Robert Shiller considers the epidemiology (spread, mutation and fading) of stories as related to economic fluctuations. He explores the 1920-21 depression, the Great Depression of the 1930s, the Great Recession of 2007-9 and the political-economic situation of today as manifestations of popular stories. Based on these examples, other examples from other fields and his experience, he concludes that: Keep Reading

Do accounting-based stock return anomalies exist in samples that precede and follow those in which researchers discover them? In their November 2016 paper entitled “The History of the Cross Section of Stock Returns”, Juhani Linnainmaa and Michael Roberts examine the robustness of 36 accounting-based stock return anomalies, with initial focus on profitability and investment factors. Anomalies tested consists of six profitability measures, four earnings quality measures, five valuation ratios, 10 growth and investment measures, five financing measures, three distress measures and three composite measures. For each anomaly, they compare pre-discovery, in-sample and post-discovery anomaly average returns, Sharpe ratios, 1-factor (market) and 3-factor (market, size, book-to-market) model alphas and information ratios. Key are previously uncollected pre-1963 data. They assume accounting data are available six months after the end of firm fiscal year and generally employ annual anomaly factor portfolio rebalancing. Using firm accounting data and stock returns for a broad sample of U.S. stocks during 1918 through December 2015, they find that: Keep Reading

How can the financial markets research community shed biases that exaggerate predictability and associated expected performance of investment strategies? In his January 2017 paper entitled “The Scientific Outlook in Financial Economics”, Campbell Harvey assesses the conventional approach to empirical research in financial economics, sharing insights from other fields. He focuses on the meaning of p-value, its limitations and various approaches to p-hacking (manipulating models/data to increase statistical significance, as in data snooping). He then outlines and advocates a Bayesian alternative approach to research. Based on research metadata and examples, he concludes that: Keep Reading

How many factors are optimal for modeling future returns of individual stocks? How do these factors relate to conventionally used factors (market, size, value, momentum, investment, profitability…)? In the June 2016 version of their paper entitled “Multifactor Models and the APT: Evidence from a Broad Cross-Section of Stock Returns”, Ilan Cooper, Paulo Maio and Dennis Philip derive mathematically an optimal set of factors for predicting returns of 278 stock portfolios created by sorting U.S. stocks into tenths (deciles) according to 28 market anomalies encompassing aspects of value, momentum, investment, profitability and intangibles. They apply asymptotic principal components analysis to these portfolios to identify the factors. They quantify the premium of each of these factors as the average return spread between extreme deciles of monthly sorts of the 278 source portfolios on the factor. They then examine interactions between this mathematical factor set and several widely used empirical multi-factor models: the Fama-French 3-factor model (market, size, book-to-market); a 4-factor model (adding momentum to the 3-factor model); a second 4-factor model (adding liquidity to the 3-factor-model); a third 4-factor model (market, size, investment, profitability); and, a 5-factor model (adding investment and profitability to the 3-factor model). Using monthly returns for the 278 source stock portfolios during January 1972 through December 2013, they find that: Keep Reading

How should investors balance expected return and expected risk in allocating between risky and risk-free assets? In their short December 2016 paper entitled “Optimal Trade Sizing in a Game with Favourable Odds: The Stock Market”, Victor Haghani and Andrew Morton apply a simple rule of thumb related to mean-variance optimization to estimate the optimal allocation to risky assets. They also note several implications of this rule. Based on assumptions about investor motivation and straightforward mathematics, they conclude that: Keep Reading

How can investors, large or small, overcome what appear to be obvious shortcomings in risk management, as occasionally indicated by portfolio crashes? In his November 2016 paper entitled “Managing Risks in Institutional Portfolios”, Andrea Malagoli critiques conventional investment portfolio risk management methodologies and offers precepts for robust risk management. He relies on a few empirical observations rather than abstract theoretical principles. Based on these observations, he concludes that: Keep Reading

Is a passive investor one who holds all securities in their respective market capitalization weights, or one who never trades? In his October 2016 paper entitled “Sharpening the Arithmetic of Active Management”, Lasse Pedersen challenges the proposition that active trading is a zero sum game that produces an average gross return equal to that realized by passive investors. He argues that holding the market capitalization-weighted portfolio over the long term requires trading as securities enter and exit the market, new shares are issued, old shares are repurchased and authorities reconstitute market indexes. In other words, the market portfolio changes over time such that even passive investors must trade, and they may trade unfavorably with active managers. Also, real passive investors trade for non-investment reasons, again perhaps unfavorably with active managers. Based on the arithmetic of realistic portfolio maintenance, he concludes that: Keep Reading

Do stock return anomalies weaken after discovery? If so, why? In the February 2016 update of their paper entitled “Does Academic Research Destroy Stock Return Predictability?”, David McLean and Jeffrey Pontiff examine out-of-sample and post-publication performance of 97 predictors of the cross section of stock returns published in peer-reviewed finance, accounting and economics journals. For each predictor, published confidence in predictive power is at least 95%, and replication is feasible with publicly available data. The publication date is year and month on the cover of the journal. Their goal is to determine the degrees to which any future degradation in predictive power derives from: (1) statistical biases (exposed out-of-sample but pre-publication); and, (2) market adaptation to strategies used by investors to exploit anomalies (exposed post-publication). For each predictor and interval, they employ a consistent test methodology based on average monthly return for a hedge portfolio that is long (short) the fifth of stocks with the highest (lowest) expected returns based on the original study. Portfolios are equally weighted unless the original study uses value weighting. Using extensions to 2013 of the exact or best available approximations of original data for the 97 predictive variables with samples starting as early as 1926 and ending as late as 2011, they find that: Keep Reading

What is the single best performance metric an investor can use to rank performances of competing portfolios (such as mutual funds)? In his September 2016 paper entitled “Measuring Portfolio Performance: Sharpe, Alpha, or the Geometric Mean?”, Moshe Levy compares Sharpe ratio, 5-factor (market, size, book-to-market, profitability, investment) alpha and geometric mean return as portfolio performance metric. The widely used Sharpe ratio is optimal when return distributions are normal and the investor can borrow at the lending (risk-free) rate without limit for leverage. However, asset return distributions may not be normal, investors generally borrow at an interest rate above the risk-free rate and Federal Reserve Regulation T restricts borrowing to 100% of an investor’s initial capital. Moreover, investors typically restrict themselves to much lower borrowing levels. His methodology is to compare the ranking of a set of actual equity mutual funds under realistic assumptions based on each of the three metrics with the ranking produced by utility maximizing allocations for each fund paired with the risk-free asset. The better the ranking produced by the metric aligns with the utility maximization ranking, the better the metric. His baseline assumption is that actual annual borrowing rate is 3.5% above the lending rate. For robustness, he considers several levels of investor risk aversion in determining utility maximization and other gaps between borrowing and lending rates. Using theory, monthly returns for 10,145 U.S. domestic equity mutual funds, the risk-free (lending) rate and returns for the five Fama-French factors during July 2005 through June 2015, he finds that: Keep Reading