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Big Ideas

These blog entries offer some big ideas of lasting value relevant for investing and trading.

Brute Force Stock Trading Signal Discovery

How serious is the snooping bias (p-hacking) derived from brute force mining of stock trading strategy variations? In their August 2017 paper entitled “p-Hacking: Evidence from Two Million Trading Strategies”, Tarun Chordia, Amit Goyal and Alessio Saretto test a large number of hypothetical trading strategies to estimate an upper bound on the seriousness of p-hacking and to estimate the likelihood that a researcher can discover a truly abnormal trading strategy. Specifically, they:

  • Collect historical data for 156 firm accounting and stock price/return variables as available for U.S. common stocks in the top 80% of NYSE market capitalizations with price over $3.
  • Exhaustively construct about 2.1 million trading signals from these variables based on their levels, changes and certain combination ratios.
  • Calculate three measures of trading signal effectiveness:
    1. Gross 6-factor alphas (controlling for market, size, book-to-market, profitability, investment and momentum) of value-weighted, annually reformed hedge portfolios that are long the value-weighted tenth, or decile, of stocks with the highest signal values and short the decile with the lowest.
    2. Linear regressions that test ability of the entire distribution of trading signals to explain future gross returns based on linear relationships.
    3. Gross Sharpe ratios of the hedge portfolios used for alpha calculations.
  • Apply three multiple hypothesis testing methods that account for cross-correlations in signals and returns (family-wise error rate, false discovery rate and false discovery proportion.

They deem a signal effective if it survives both statistical hurdles (alpha t-statistic 3.79 and regression t-statistic 3.12) and has a monthly Sharpe ratio higher than that of the market (0.12). Using monthly values of the 156 specified input variables during 1972 through 2015, they find that:

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A Few Notes on Trend Following

Michael Covel prefaces the 2017 Fifth Edition of his book, Trend Following: How to Make a Fortune in Bull, Bear, and Black Swan Markets, by stating that: “The 233,092 words in this book are the result of my near 20-year hazardous journey for the truth about this trading called trend following. …Trend following…aims to capture the majority of a connected market trend up or down for outsize profit. It is designed for potential gain in all major asset classes–stocks, bonds, metals, currencies, and hundreds of other commodities. …if you want outside-the-the-box different, the truth of how out-sized returns are made without any fundamental predictions or forecasts, this is it. And if you want the honest data-driven proof, I expect my digging will give everyone the necessary confidence to break their comfort addiction to the box they already know and go take a swing at making a fortune…” Based on his experience as a trader/portfolio manager and the body of trend following research, he concludes that: Keep Reading

Financial Markets as Massively Multiplayer Gambling

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

The Power of Stories?

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

Robustness of Accounting-based Stock Return Anomalies

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

Remedies for Publication Bias, Poor Research Design and p-Hacking?

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

Perfect Factor Model of U.S. Stock Returns?

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 Much to Risk?

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

Manage Risk by Challenging Assumptions

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

Real-world Passive vs. Active

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

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