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Asset Pricing Models and Market Efficiency

Using Machine Learning to Explain Stock Market Anomalies

  • 2026
  • Book

About this book

This book shows that the stock market returns of hundreds of anomaly portfolios discovered by researchers in finance over the past three decades can be explained by a recent asset pricing model dubbed the ZCAPM. Anomaly portfolios are long/short portfolio returns on stocks that cannot be explained by asset pricing models, and their number has been steadily increasing into the hundreds. Since asset pricing models cannot explain them, behavioral theories have become popular to account for anomalies. Unlike the efficient market hypothesis that assumes rational investors, these human psychology-based theories emphasize irrational investor behavior.

This book collects and analyzes a large database of U.S. stock returns for anomaly portfolios over a long sample period spanning approximately 60 years. The authors overview different asset pricing models that have attempted to explain anomalous portfolio returns in the stock market. They then provide a theoretical and empirical discussion of a new asset pricing model dubbed the ZCAPM and report compelling empirical evidence that reveals the ZCAPM can explain hundreds of anomalies. Implications to the efficient-markets/behavioral-finance controversy are discussed. The book will be of particular interest to researchers, students, and professors of capital markets, asset management, and financial economics alongside professionals.

Table of Contents

  1. Frontmatter

  2. Introduction

    1. Frontmatter

    2. Chapter 1. The Rise of Anomalies: Challenging Theory and Practice in Finance

      James W. Kolari, Wei Liu, Jianhua Z. Huang, Huiling Liao
      The chapter delves into the debate between the efficient markets hypothesis (EMH) and behavioral finance, focusing on the role of anomalies in stock market returns. It begins by discussing the efficient markets hypothesis (EMH) and the Capital Asset Pricing Model (CAPM), which posits that security prices fully reflect all available information. The chapter then explores how anomalies, such as the size and value effects, challenge the CAPM and lead to the development of multifactor models by Fama and French. The text also examines the rise of behavioral finance, which argues that human psychology plays a significant role in explaining stock market anomalies. The chapter introduces the ZCAPM model, which uses machine learning to explain a large number of anomaly portfolios, providing strong support for the EMH. The chapter concludes by discussing the implications of these findings for the debate between efficient markets and behavioral finance, highlighting the need for further research to replicate and expand on these results.
    3. Chapter 2. Anomaly Stock Portfolios

      James W. Kolari, Wei Liu, Jianhua Z. Huang, Huiling Liao
      This chapter delves into the fascinating world of anomaly stock portfolios, examining why many anomalies seem to disappear over time. Key topics include the impact of statistical bias and market arbitrage on anomaly returns, the role of publication bias, and the replicability of anomalies across different studies. The chapter also explores the economic significance of anomalies and their potential as tradable investment strategies. Recent research suggests that anomalies are not merely a product of data mining but persist when considering risk-adjusted returns and accurate information. The chapter concludes that while anomalies are real, their practical application in investment strategies is limited due to trading costs and post-publication effects.
  3. Anomalies Literature and Asset Pricing Models

    1. Frontmatter

    2. Chapter 3. Prominent Asset Pricing Models and Anomaly Portfolio Returns

      James W. Kolari, Wei Liu, Jianhua Z. Huang, Huiling Liao
      This chapter delves into the prominent asset pricing models and their ability to explain anomaly portfolio returns. It begins with the Fama-French three-factor model, which introduced size and value factors to better explain stock returns compared to the Capital Asset Pricing Model (CAPM). The chapter then explores the Carhart four-factor model, which adds a momentum factor to account for momentum anomalies. Further, it discusses the Fama-French five-factor model, which incorporates profitability and capital investment factors, and the subsequent six-factor model that includes a momentum factor. The text also covers alternative models like the Hou-Xue-Zhang four-factor model and the Stambaugh-Yuan four-factor model, which introduce different factors such as management and performance. Additionally, it touches on the Lettau-Pelger latent five-factor model, which uses Principal Component Analysis to identify asset pricing factors. The chapter concludes by highlighting the ongoing challenges in asset pricing models and the potential for future developments, including the ZCAPM model by Kolari, Liu, and Huang. Readers will gain insights into the evolution of asset pricing models, the role of various factors in explaining stock returns, and the current debates and advancements in the field.
    3. Chapter 4. The ZCAPM and Previous Tests of Anomaly Portfolio Returns

      James W. Kolari, Wei Liu, Jianhua Z. Huang, Huiling Liao
      The chapter delves into the ZCAPM, a groundbreaking asset pricing model derived from Black's zero-beta CAPM. It introduces two key factors: the market factor and the cross-sectional market volatility factor, both estimable from daily market data. The ZCAPM's theoretical framework is explored, highlighting its unique geometry and the role of market dispersion in reaching the efficient frontier. Empirical tests demonstrate the ZCAPM's impressive performance, outperforming well-known multifactor models in predicting anomaly portfolio returns. The chapter also discusses the innovative use of machine learning techniques, such as the expectation-maximization algorithm, to estimate hidden variables and improve predictive accuracy. The ZCAPM's ability to explain a wide range of anomaly returns is thoroughly examined, providing compelling evidence for its validity as an asset pricing model. The chapter concludes with a summary of the ZCAPM's strengths and its potential to revolutionize asset pricing in the finance literature and profession.
  4. Explaining Anomaly Portfolio Returns

    1. Frontmatter

    2. Chapter 5. The ZCAPM and Large Online Datasets of Anomaly Portfolio Returns

      James W. Kolari, Wei Liu, Jianhua Z. Huang, Huiling Liao
      This chapter delves into the performance of the Zero-Crossing Asset Pricing Model (ZCAPM) in explaining anomaly portfolio returns, comparing it to various multifactor models. The study uses large online datasets of anomaly portfolio returns and conducts out-of-sample cross-sectional regression tests. The results show that the ZCAPM significantly outperforms other models, with higher goodness-of-fit and lower mispricing errors. The chapter also explores the implications of these findings for market efficiency and asset pricing theories. It suggests that the ZCAPM can be a unifying model that links general equilibrium models to empirically designed multifactor models. The analysis highlights the importance of market return dispersion in explaining anomaly returns and supports the efficient market hypothesis. The chapter concludes with recommendations for future research, including replication studies, exploring unpriced anomalies, event studies, corporate finance applications, portfolio management, determinants of market return dispersion, and extending tests to other asset classes.
    3. Chapter 6. Further Tests of Asset Pricing Models and Anomaly Portfolio Returns

      James W. Kolari, Wei Liu, Jianhua Z. Huang, Huiling Liao
      This chapter delves into the performance of various asset pricing models in explaining the returns of different portfolios, including those based on firm and stock characteristics, industry portfolios, and anomaly portfolios in Japan. The study employs out-of-sample Fama-MacBeth cross-sectional regressions and graphical analyses of average mispricing errors to evaluate models like CAPM, Fama-French three-, five-, and six-factor models, Carhart four-factor model, Hou-Xue-Zhang four-factor q model, and Stambaugh-Yuan four-factor model. A key finding is the consistent outperformance of the ZCAPM model, which demonstrates superior explanatory power and statistical significance in its factor loadings. The ZCAPM's ability to explain both long/short anomaly portfolio returns and their constituent portfolios suggests its potential as a more valid asset pricing model. The chapter also highlights the challenges in pricing industry portfolios and calls for further research to understand their unique dynamics. The empirical evidence supports the efficient markets hypothesis and questions the need for behavioral explanations in finance.
  5. Asset Pricing Model Validity

    1. Frontmatter

    2. Chapter 7. Empirical Tests on the Validity of Asset Pricing Models

      James W. Kolari, Wei Liu, Jianhua Z. Huang, Huiling Liao
      This chapter delves into the empirical testing of asset pricing models, focusing on the validity of models like CAPM and multifactor models. The study introduces a new alpha test based on out-of-sample cross-sectional regression analyses, addressing the limitations of traditional in-sample tests. Key findings include the significance of missing factors in most models and the superior performance of the ZCAPM, which shows minimal mispricing errors. The research also highlights the importance of out-of-sample testing in identifying missing factors and validating asset pricing models. The study concludes that the ZCAPM is a robust model, efficiently capturing systematic risk factors and suggesting market efficiency. The chapter provides valuable insights into the ongoing search for missing factors in asset pricing models and the potential discontinuation of this search if the ZCAPM's performance is confirmed.
  6. Conclusion

    1. Frontmatter

    2. Chapter 8. Machine Learning in Asset Pricing: The Dominance of the ZCAPM

      James W. Kolari, Wei Liu, Jianhua Z. Huang, Huiling Liao
      This chapter delves into the transformative impact of machine learning on asset pricing, with a focus on the Zero-Beta CAPM (ZCAPM). The ZCAPM, which utilizes the mean market return and cross-sectional return dispersion as its factors, is shown to outperform traditional multifactor models in explaining stock market anomalies. The chapter reviews the theoretical derivation and empirical specification of the ZCAPM, highlighting its use of the expectation-maximization algorithm to estimate hidden variables. Extensive out-of-sample tests with large datasets of anomaly portfolios demonstrate the ZCAPM's exceptional explanatory power, even for challenging momentum portfolios. The chapter also discusses the implications for future asset pricing research and market efficiency, suggesting areas for further development and study. The findings support the efficient market hypothesis and challenge the need for behavioral theories to explain anomaly portfolio returns.
  7. Backmatter

Title
Asset Pricing Models and Market Efficiency
Authors
James W. Kolari
Wei Liu
Jianhua Z. Huang
Huiling Liao
Copyright Year
2026
Electronic ISBN
978-3-031-92901-4
Print ISBN
978-3-031-92900-7
DOI
https://doi.org/10.1007/978-3-031-92901-4

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