Decision-making under Market Indeterminacy

The Efficient Markets Hypothesis (EMH) is the focusing topic in the past 50 years of financial market researches. Many empirical studies are then provided that want to test EMH but have no consensus. The perception of EMH determines the attitude and strategy of participants and regulators in financial market. One perception of EMH argues that investors’ behavior of seeking abnormal profits and arbitrage drives prices to their ‘‘correct’’ value. Investigating the “correct” value derives the concept of “market indeterminacy”. It means the inability to determine whether stock prices are efficient or inefficient. Market indeterminacy pervades stock markets because “correct” prices are unknown because of imperfect information and model sensitivity. Market indeterminacy makes arbitrage risky and makes event studies unreliable in some policy and litigation applications. The concept of market efficiency is needed to be re-recognized considering the mechanism of price formation. In order to further research and practice in law and financial market, there needs a view from the “jumping together” of disparate disciplines. Adaptive Markets Hypothesis(AMH) that using the evolutionary principles in financial market is a new viewpoint oncognitive decision and deserves to be paid more attention to.

A New Measure of Market Inefficiency

Financial crises, such as the Great Financial Crisis of 2007–2009 and the COVID-19 Crisis of 2020–2021, lead to high volatility in financial markets and highlight the importance of the debate on the Efficient Markets Hypothesis, a corollary of which is that in an efficient market it should not be possible to systematically make excess returns. In this paper, we discuss a new empirical measure—Excess Trading Returns—that distinguishes between market and trading returns and that can be used to measure inefficiency. We define an Inefficiency Matrix that can provide a complete, empirical characterization of the inefficiencies inherent in a market. We illustrate its use in the context of empirical data from a pair of model markets, where information asymmetries can be clearly understood, and discuss the challenges of applying it to market data from commercial exchanges.

Efficient Markets Hypothesis in the time of COVID-19.

This paper examines how the largest stock market of the world, the U.S., and particularly the S&P500 index, reacted during the COVID-19 outbreak (02.01.2020-30.04.2020). Using simple financial and corporate analysis (adopting Constant Growth Model) procedures for our theoretical framework, we juxtapose the released news with the respective market performance in order to examine if the stock market always incorporated the available information in time. We show that the market in some sub-periods was not moving as it was expected, and the runs-test statistically confirmed our assumptions that the US stock market was not efficient during the COVID-19 outbreak. We find that in some cases the market does not incorporate the news instantly, is irrational, and non-sensible. All these make the market’s behavior unpredictable for a rational asset pricing model because as this paper shows even the simplest financial theories could explain rational behavior, but the market presented a different performance.

Anomalous Behaviour and Volatility in Stock Returns are still Live - Efficient Markets Hypothesis? : Perspective from Pakistan Stock Exchange (PSX)

Purpose: This empirical study investigates the anomalous behaviour and volatility in stock return of PSX-100 index of Pakistan Stock Exchange (PSX). Design/Methodology/Approach: The data is taken from January, 2006 to December, 2018 to detect variability and predictability of stock returns. ARCH and GARCH models are applied to check the volatility in stock returns using dummy variable. Findings: It is found that there exists positive and significant September effect in Pakistani equity market. The returns are high in the month of September than other months. The constant returns do not exist during the whole year so the efficient market hypothesis contradicts. Implications/Originality/Value: The Efficient Market Hypothesis is question mark due to volatility for mispricing the securities. The mispricing may have implications for undervalue or overvalue the securities and overall economic activity of equity – stock returns.

BEHAVIORAL FINANCE: EMPIRICAL EVIDENCE USING MAGIC FORMULA IN THE BRAZILIAN STOCK MARKET

ABSTRACT Purpose: Explain the causes of inefficiencies in asset pricing on the Brazilian stock exchange through the behavioral finance hypothesis. Originality/value: Research made in the stock market over the last decades suggests that there is evidence of obtaining returns above the market average, through the purchase of undervalued assets, that is, when it has a low relation between the price and the fundamentals of the company. However, there is a notable discrepancy regarding the interpretation of causes among academics. The efficient markets hypothesis was presented, which is based on the premise of the strict rationality of economic agents. On the other hand, the behavioral finance theory was also discussed, which presents different assumptions. Design/methodology/approach: Using the historical quotes of the shares traded on B3, extracted from economática(r)'s database, the present work used the Magic Formula methodology to investigate the behavioral effect through the inefficiencies found in the pricing of these assets. Findings: The results suggest that the Brazilian stock market, in conformity with works of the same nature performed in markets in other countries, has inefficiencies in the pricing of assets, so that it is possible to obtain advantages from economic agents. The interpretation for the causes of such inefficiencies is based on the premises of behavioral finance, and points to the existence of a limitation in the rationalization of these agents.

Nonlinearity in financial series: transitory or permanent?

In this article we present evidence that nonlinearity episodes in financial series are more permanent than transitory. At the same time, these episodes show different behaviors depending on the market analyzed, which would indicate that they are not completely synchronized. On the other hand, the size of the window for detecting nonlinear episodes has an impact on the number of nonlinear windows found, as well as the percentage of nonlinear windows with respect to the total number of windows, confirming a window size effect. The results strongly invalidate the efficient markets hypothesis and forcefully explain the incapability to predict its future values.