scholarly journals PORTUGUESE STOCK MARKET: A LONG-MEMORY PROCESS?

2011 ◽  
Vol 12 (1) ◽  
pp. 75-84 ◽  
Author(s):  
Sameer Rege ◽  
Samuel Gil Martín
Keyword(s):  
Stock Market ◽  
Stock Prices ◽  
Long Memory ◽  
Hurst Exponent ◽  
Linear Trend ◽  
Fluctuation Analysis ◽  
Generation Process ◽  
Data Generation ◽  
Data Generation Process ◽  
Daily Returns

This paper gives a basic overview of the various attempts at modelling stochastic processes for stock markets with a specific application to the Portuguese stock market data. Long-memory dependence in the stock prices would completely alter the data generation process and econometric models not considering the long-range dependence would exhibit poor forecasting abilities. The Hurst exponent is used to identify the presence of long-memory or fractal behaviour of the data generation process for the daily returns to ascertain if the process follows a fractional brownian motion. Detrended fluctuation analysis (DFA) using linear and quadratic trends and the Geweke Porter-Hudak methods are applied to detect the presence of long-memory or persistence. We find that the daily returns exhibit a small amount of long memory and that the quadratic trend used in the DFA overestimates the value of the Hurst exponent. These findings are corroborated by the use of the Geweke Porter-Hudak method wherein the Hurst exponent is close to the DFA using the linear trend.

Predictability of China’s Stock Market Returns Based on Combination of Distribution Forecasting Models

2020 ◽  
Vol 24 (4) ◽  
pp. 477-487
Author(s):  
Yanyun Yao ◽  
Xiutian Zheng ◽  
Huimin Wang ◽  
◽  
Keyword(s):  
Stock Market ◽  
Stock Prices ◽  
Nonparametric Model ◽  
Equal Weight ◽  
Generation Process ◽  
Data Generation ◽  
Model Combination ◽  
Combination Strategy ◽  
Stock Market Returns ◽  
Score Combination

No consensus exists in the literature on whether stock prices can be predicted, with most existing studies employing point forecasting to predict returns. By contrast, this study adopts the new perspective of distribution forecasting to investigate the predictability of the stock market using the model combination strategy. Specifically, the Shanghai Composite Index and the Shenzhen Component Index are selected as research objects. Seven models – GARCH-norm, GARCH-sstd, EGARCH-sstd, EGARCH-sstd-M, one-component Beta-t-EGARCH, two-component Beta-t-EGARCH, and the EWMA-based nonparametric model – are employed to perform distribution forecasting of the returns. The results of out-of-sample forecasting evaluation show that none of the individual models is “qualified” in terms of predictive power. Therefore, three combinations of individual models were constructed: equal weight combination, log-likelihood score combination, and continuous ranked probability score combination. The latter two combinations were found to always have significant directional predictability and excess profitability, which indicates that the two combined models may be closer to the real data generation process; from the perspective of economic evaluation, they may have a predictive effect on the conditional return distribution in China’s stock market.

scholarly journals Searching for long memory effects in time series of central Europe stock market indices

2008 ◽  
Vol 56 (3) ◽  
pp. 187-200
Author(s):  
Luboš Střelec
Keyword(s):  
Time Series ◽  
Stock Market ◽  
Central Europe ◽  
Long Memory ◽  
Hurst Exponent ◽  
Financial Time Series ◽  
Memory Effects ◽  
Stock Index ◽  
Source Data ◽  
Independent Process

This article deals with one of the important parts of applying chaos theory to financial and capital markets – namely searching for long memory effects in time series of financial instruments. Source data are daily closing prices of Central Europe stock market indices – Bratislava stock index (SAX), Budapest stock index (BUX), Prague stock index (PX) and Vienna stock index (ATX) – in the period from January 1998 to September 2007. For analysed data R/S analysis is used to calculate the Hurst exponent. On the basis of the Hurst exponent is characterized formation and behaviour of analysed financial time series. Computed Hurst exponent is also statistical compared with his expected value signalling independent process. It is also operated with 5-day returns (i.e. weekly returns) for the purposes of comparison and identification nonperiodic cycles.

The problem of the missing dead

2020 ◽  
pp. 002234332096215
Author(s):  
Sophia Dawkins
Keyword(s):  
Human Rights ◽  
South Sudan ◽  
Generation Process ◽  
Data Generation ◽  
Social Scientists ◽  
Data Generation Process ◽  
South Sudanese ◽  
Point Estimates ◽  
Source Data ◽  
Cross National

This article examines what scholars can learn about civilian killings from newswire data in situations of non-random missingness. It contributes to this understanding by offering a unique view of the data-generation process in the South Sudanese civil war. Drawing on 40 hours of interviews with 32 human rights advocates, humanitarian workers, and journalists who produce ACLED and UCDP-GED’s source data, the article illustrates how non-random missingness leads to biases of inconsistent magnitude and direction. The article finds that newswire data for contexts like South Sudan suffer from a self-fulfilling narrative bias, where journalists select stories and human rights investigators target incidents that conform to international views of what a conflict is about. This is compounded by the way agencies allocate resources to monitor specific locations and types of violence to fit strategic priorities. These biases have two implications: first, in the most volatile conflicts, point estimates about violence using newswire data may be impossible, and most claims of precision may be false; secondly, body counts reveal little if divorced from circumstance. The article presents a challenge to political methodologists by asking whether social scientists can build better cross-national fatality measures given the biases inherent in the data-generation process.

Stock prices' long memory in China and the United States

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Zhengxun Tan ◽  
Yao Fu ◽  
Hong Cheng ◽  
Juan Liu
Keyword(s):  
Stock Market ◽  
Stock Prices ◽  
Long Memory ◽  
Stock Markets ◽  
Information Disclosure ◽  
Structural Breaks ◽  
Efficient Market Hypothesis ◽  
The United States ◽  
Chinese Stock Market ◽  
Content Type

PurposeThis study aims to examine the long memory as well as the effect of structural breaks in the US and the Chinese stock markets. More importantly, it further explores possible causes of the differences in long memory between these two stock markets.Design/methodology/approachThe authors employ various methods to estimate the memory parameters, including the modified R/S, averaged periodogram, Lagrange multiplier, local Whittle and exact local Whittle estimations.FindingsChina's two stock markets exhibit long memory, whereas the two US markets do not. Furthermore, long memory is robust in Chinese markets even when we test break-adjusted data. The Chinese stock market does not meet the efficient market hypothesis (EMHs), including the efficiency of information disclosure, regulations and supervision, investors' behavior, and trading mechanisms. Therefore, its stock prices' sluggish response to information leads to momentum effects and long memory.Originality/valueThe authors elaborately illustrate how long memory develops by analyzing not only stock market indices but also typical individual stocks in both the emerging China and the developed US, which diversifies the EMH with wider international stylized facts and findings when compared with previous literature. A couple of tests conducted to analyze structural break effects and spurious long memory demonstrate the reliability of the results. The authors’ findings have significant implications for investors and policymakers worldwide.

TIME-VARYING LONG MEMORIES OF THE CHINESE CURRENCY AND STOCK MARKETS BASED ON THE HURST EXPONENT

2014 ◽  
Vol 13 (01) ◽  
pp. 1450007 ◽  
Author(s):  
CAO GUANGXI ◽  
HAN YAN ◽  
CUI WEIJUN
Keyword(s):  
Exchange Rate ◽  
Stock Market ◽  
Stock Markets ◽  
Hurst Exponent ◽  
Composite Index ◽  
Fluctuation Analysis ◽  
Time Varying ◽  
Chinese Stock Market ◽  
Currency Market ◽  
Cointegration Tests

Based on the daily return and volatility series of the Chinese yuan (RMB)/US dollar (USD) exchange rate and the Shanghai Stock Composite Index, the time-varying long memories of the Chinese currency and stock markets are investigated by comprehensively using the rescaled range (R/S), the modified R/S, and the detrended fluctuation analysis methods. According to the results drawn: (1) the efficiency of the Chinese currency market has not improved significantly, whereas the efficiency of the Chinese stock market has improved steadily, (2) volatility series presents longer memory than return series either in the Chinese currency or stock market and (3) the time-varying Hurst exponent of the Chinese currency market is sensitive to the reform that enhances the flexibility of the RMB exchange rate. Moreover, we find that short-term bidirectional Granger causal relationship exists, but no long-run equilibrium relationship between the time-varying Hurst exponents of the Chinese currency and stock markets was found based on the Granger causality and cointegration tests, respectively.

Trading Volume and Cross-Autocorrelations of Stock Returns in Emerging Markets: Evidence from the Taiwan Stock Market

2004 ◽  
Vol 07 (04) ◽  
pp. 509-524
Author(s):  
Wen-Hsiu Kuo ◽  
Hsinan Hsu ◽  
Chwan-Yi Chiang
Keyword(s):  
Stock Market ◽  
Stock Returns ◽  
Stock Prices ◽  
Trading Volume ◽  
Price Limits ◽  
Speed Of Adjustment ◽  
New Information ◽  
Weak Evidence ◽  
Market Inefficiency ◽  
Daily Returns

This study empirically investigates the interaction between trading volume and cross-autocorrelations of stock returns in the Taiwan stock market. The result shows that returns on high trading volume portfolios lead returns on low trading volume portfolios when controlled for firm size, indicating that trading volume determines lead-lag cross-autocorrelations of stock returns. Overall, the empirical findings of this study demonstrate similar results for both monthly and daily returns, suggesting that nonsynchronrous trading is not the main reason for the lead-lag cross-autocorrelations presented in this study. Consequently, the empirical results presented here support the speed of adjustment hypothesis, and suggest that some market inefficiency exists in the Taiwan stock market. Additionally, compared with evidence of lead-lag cross-autocorrelations in the larger, less regulated US stock market, as examined by Chordia and Swaminathan (2000), Taiwan stock market displays less evidence of VARs and Dimson beta regressions. We conjecture that this weak evidence may result from the regulations limiting daily price movements in the Taiwan stock market. Although the price limits policy lowers risk and stabilizes stock prices, it also prevents stock prices and trading volume from instantaneously and fully reflecting new information.

scholarly journals Testing for efficiency in the Saudi stock market: does corporate governance change matter?

2020 ◽  
Author(s):  
Mamdouh Abdulaziz Saleh Al-Faryan ◽  
Everton Dockery
Keyword(s):  
Corporate Governance ◽  
Stock Market ◽  
Stock Prices ◽  
Hurst Exponent ◽  
Weak Form ◽  
Long Range Dependence ◽  
Informational Efficiency ◽  
Variance Ratio ◽  
Wald Tests ◽  
Random Walk Hypothesis

Abstract We study the informational efficiency of the Saudi stock market (SSM), while accounting for corporate governance change, based on single, multiple, and variance ratio-based WALD tests and runs test. The main findings indicate that when the whole period is considered, the random walk hypothesis is rejected, but when divided into two sub-periods separated by the pre-corporate governance and the period marked by corporate governance change, the analysis demonstrates sub-period improvement in weak-form efficiency for the examined series. Robustness of results is verified by analysis using sector indices, which point to market efficiency. Interestingly, Hurst Exponent estimates evidence long-range dependence which suggests the predictability of stock prices and the prospect of speculative opportunities.

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