Especially after the 90ies, where the stock markets raised enormously, many private investors joined the stock market and were blended by abnormal profits and neglected possible losses. The same behavior could be observed before the Financial Crisis became reality. But each endless raising stock market would finally collapse, because stock prices are randomly and only driven by relevant news. The adjustment to the news is quickly. This is the theoretical argumentation of the Efficient Market Hypothesis (EMH), which will be evaluated in this paper.
The author gives an overview about the EMH by explaining the basic principles and its mathematical formulation. The practical part evaluated the EMH on selected examples, where the theory could only be partly approved.
Table of Contents
1 Introduction
2 The Efficient Market Hypothesis
2.1 Definition
2.2 Tests
2.2.1 Test of weak efficiency
2.2.2 Test of semi-strong efficiency
2.2.3 Test of strong efficiency
2.3 Mathematical Description
2.3.1 Introduction to Stochastic Processes
2.3.2 General concept of the EMH
2.3.3 Martingale – model
2.3.4 Random Walk – model
2.3.5 CAP – model
2.3.6 Resume
3 Application to Stock Markets
3.1 General behavior of stock markets
3.2 Tests of weak efficiency
3.3 Test of semi-strong efficiency
4 Criticism
4.1 Rationality
4.2 Market Anomalies
4.3 Joint Hypothesis
5 Outlook
6 Conclusion
Objectives and Core Topics
This paper aims to provide a critical introduction to the Efficient Market Hypothesis (EMH) through a combination of verbal and mathematical analysis. The core objective is to evaluate whether financial markets operate efficiently by comparing theoretical models with empirical stock market data.
- Explanation of EMH principles and forms (weak, semi-strong, strong).
- Mathematical formulation of market efficiency using stochastic processes.
- Empirical evaluation of market data from the DAX, Continental AG, and Lehman Brothers.
- Critical discussion of rational agent assumptions and market anomalies.
- Analysis of modern financial modeling techniques like ARCH/GARCH.
Excerpt from the Book
2.3.1 Introduction to Stochastic Processes
The formal description of the EMH depends on the assumption that profits can be displayed as random variables. A random variable is a function X that related a real number x according to the result of a random experiment. The outcome of this individual random experiment x isn’t affected by any previous outcome and cannot be predicted with certainty. The outcome x can be adopted to different values x1, x2,…, xn. The frequency of occurrence will be described by the probability density function f(x).
The stock prices can be understood as one certain realization dependent from the time variable t (1, 2,…,t). This sequence of a random variable Xt is called a stochastic process. A process is called weak stationary, if the first and second moment is constant in time (strong stationary if all moments are constant).
Figure 1 shows a wiener process as a typical example for a stochastic process.
Finally, it should be mentioned that the observed stock prices are only one possible realization of a stochastic process. Therefore it’s not possible to calculate the expectation µt or the variance σ²t of the process, because the probability density function is unknown in order to calculate these and higher moments. For that reason mathematical models have to develop in order to describe the EMH.
Summary of Chapters
1 Introduction: Introduces the controversy surrounding stock market predictability and defines the scope of the paper regarding the Efficient Market Hypothesis.
2 The Efficient Market Hypothesis: Details the theoretical definitions, different forms of efficiency, and the mathematical framework including stochastic models and the "fair game" condition.
3 Application to Stock Markets: Analyzes empirical market data (DAX, Lehman Brothers, Continental AG) to test market efficiency and evaluate volatility clusters.
4 Criticism: Addresses the challenges to EMH, specifically focusing on bounded rationality, market anomalies, and the "joint hypothesis problem".
5 Outlook: Discusses the emergence of Behavior Finance as an alternative to classical efficient market theories.
6 Conclusion: Synthesizes the findings, concluding that empirical data often indicates market inefficiency rather than perfect efficiency.
Keywords
Efficient Market Hypothesis, EMH, Stock Markets, Stochastic Processes, Random Walk, Arbitrage, Market Anomalies, Behavioral Finance, DAX, Autocorrelation, Volatility, Financial Modeling, Rationality, Joint Hypothesis Problem, ARCH Models
Frequently Asked Questions
What is the primary focus of this paper?
The paper examines the validity of the Efficient Market Hypothesis by contrasting its theoretical assumptions with real-world stock market performance.
What are the central themes discussed in this work?
The central themes include the definition of market efficiency, the mathematical modeling of stock prices, empirical tests of efficiency, and the critique of rational investor behavior.
What is the core research question?
The paper investigates whether financial markets are efficient and whether future stock developments can be predicted based on historical information.
Which scientific methods are utilized?
The author uses statistical and mathematical methods, including autocorrelation analysis, spectral analysis, filter techniques, and event studies, to test the EMH against empirical data.
What topics are covered in the main section?
The main section covers the mathematical foundations of stochastic processes, the "fair game" condition, tests for different forms of efficiency, and an empirical analysis of various stock indices and companies.
Which keywords define this research?
The research is characterized by terms like EMH, Random Walk, Market Anomalies, and Behavioral Finance.
What does the "Joint Hypothesis Problem" imply for the study?
It implies that any empirical test of the EMH is simultaneously testing an underlying equilibrium model, making it impossible to definitively attribute results to market inefficiency rather than an incorrect model.
How does the author evaluate the "semi-strong" form of efficiency in practice?
The author uses event studies, specifically analyzing the stock price reaction of Continental AG to the takeover offer by the Schaeffler Group, to observe how quickly information is incorporated into prices.
- Citar trabajo
- Dr.-Ing. Sebastian Harder (Autor), 2008, The Efficient Market Hypothesis and its Application to Stock Markets, Múnich, GRIN Verlag, https://www.grin.com/document/158375
