• Journal of the Korean Operations Research and Management Science Society
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• v.38 no.4
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• pp.11-33
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• 2013

We analyzed the structures and properties of the global financial market networks using social network analysis approach. The Minimum Spanning Tree (MST) lengths and networks of the global financial markets based on the correlation coefficients have been analyzed. Firstly, similar to the previous studies on the global stock indices using MST length, the diversification effects in the global multi-asset portfolio can disappear during the crisis as the correlations among the asset class and within the asset class increase due to the system risks. Second, through the network visualization, we found the clustering of the asset class in the global financial markets network, which confirms the possible diversification effect in the global multi-asset portfolio. Meanwhile, we found the changes in the structure of the network during the crisis. For the last one, in terms of the degree centrality, the stock indices were the most influential to other assets in the global financial markets network, while in terms of the betweenness centrality, Gold, Silver and AUD. In the practical perspective, we propose the methods such as MST length and network visualization to monitor the change of the correlation risk for the risk management of the multi-asset portfolio.

• Journal of the Korean Data and Information Science Society
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• v.24 no.4
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• pp.669-677
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• 2013

Quasi-Monte Carlo method is known to have lower convergence rate than the standard Monte Carlo method. Quasi-Monte Carlo methods are using low discrepancy sequences as quasi-random numbers. They include Halton sequence, Faure sequence, and Sobol sequence. In this article, we compared standard Monte Carlo method, quasi-Monte Carlo methods and three scrambling methods of Owen, Faure-Tezuka, Owen-Faure-Tezuka in valuation of multi-asset European call option through simulations. Moro inversion method is used in generating random numbers from normal distribution. It has been shown that three scrambling methods are superior in estimating option prices regardless of the number of assets, volatility, and correlations between assets. However, there are no big differences between them.

• Journal of the Korean Data and Information Science Society
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• v.17 no.4
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• pp.1099-1106
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• 2006

This study is an analysis of the stock trading value in terms of investor types in the Korean stock market for recent 12 years. We examined the characteristics in stock trading value variation according to each investor type and the interactive relationship in the trading value between types of investors. The results show that the trading value scale of every investor type increases overall while the proportion of the trading value by each investor type in the market exhibits variation. In addition, a statistically significant interactive relationship in the trading value between types of investors exists: the correlations are formed differently before and after events which largely influence the stock market.

• Journal of the Korean Data and Information Science Society
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• v.21 no.3
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• pp.407-417
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• 2010

In Basel II compliance, internal rating systems are allowed for banks to enhance the self control and the validation of the system are getting more important. The validation methods are composed of qualitative test and quantitative test, three basic standards of which are discriminatory power, stability and calibration. The aim of this article is to review the quantitative tests for calibration and find a new method for it. These methods for discrimination between forecasted PD and observed PD include binomial test, chi square test, Brier score, traffic lights approach, normal test and extended traffic lights approach. We introduce a modified extended traffic lights approach considering asset correlations.

• Journal of Distribution Science
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• v.14 no.12
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• pp.129-139
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• 2016

Purpose - This paper examines the explanatory power of the agency theory in the determination of cash holdings for Korean retail firms. If the agency theory holds, a firm with strong corporate governance structure tends to have low cash holdings. A strong governance structure makes the CEO of this firm to behave in the interests of shareholders and thus the CEO has low incentive to stockpile cash holdings, which can be easily diverted for the CEO's own managerial purposes. We investigate this relationship between corporate governance structure and cash holdings, by using corporate governance scores as a proxy variable that captures the effectiveness of corporate governance mechanism. Research design, data, and methodology - We adopt the sample of publicly listed retail firms in KOSPI market from 2005 to 2013. Financial and accounting statements are gathered from the WISEfn database. We also use the corporate governance scores published by Korean Corporate Governance Service. The relationship between the corporate governance scores and cash holdings is cross-sectionally estimated based on the ordinary least square method. This estimation method is widely accepted in the existing literature. The sample of large conglomerates, Chebol, and the remainder firms are separately examined as well, to account for the distinctive internal financing environment in these large conglomerates. Results - We mainly contribute to the extant literature by providing empirical evidence against the agency theory of cash policy. Unlike the prediction of agency theory, we confirm statistically insignificant or even positive correlations between the set of corporate governance scores and cash-asset ratios. Almost all the major corporate governance attributes including total score, shareholder rights, board structure, and the quality of information disclosure do not show negative correlations with cash holdings, which poses a strong challenge to the validity of the agency theory in the determination of retail firms' cash holdings. Conclusions - This study presents interesting empirical results with respect to the cash policy in Korean retail firms. Consistent to prior studies, I verify that the agency theory only limitedly explains the level of cash holdings. Future studies may obtain more robust results by examining a longer sample period.

• Korea Journal of Hospital Management
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• v.6 no.2
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• pp.22-36
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• 2001

The hospital bankruptcy rate is increasing, therefore it is very important to predict the bankruptcy using the existing hospital management information. The hospital bankruptcy is often measured in year intervals, called grouped duration data, not by the continuous time elapsed to the bankruptcy. This study introduces a hierarchical generalized linear model(HGLM) for analysis of hospital bankruptcy data. The hazard function for each hospital may be influenced by unobservable latent variables, and these unknown variables are usually termed as random effects or frailties which explain correlations among repeated measures of the same hospital and describe individual heterogeneities of hospitals. Practically, the data of twenty bankrupt and sixty profitable hospitals were collected for five years, and were fitted to HGLM. The results were compared with those of the logit model. While the logit model resulted only in the effects of explanatory variables on the bankruptcy status at specific period, the HGLM showed variables with significant effects over all observed years. It is concluded that the HGLM with a fixed ratio and a period of total asset turnrounds was justified, and could find significant within and between hospital variations.

• Asia-Pacific Journal of Business
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• v.13 no.2
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• pp.123-138
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• 2022

Purpose - This study compares the performances of dynamic asset allocation strategies using Korean stocks and U.S. dollar, which have been negatively correlated for a long time, to examine the diversification effects in the portfolios of them. Design/methodology/approach - In the current study, we use KOSPI200 index, as a proxy of the aggregated portfolio of Korean stocks, and USDKRW foreign exchange rate to implement various portfolio management strategies. We consider the equally-weighted, risk-parity, minimum variance, most diversified, and growth optimal portfolios for comparison. Findings - We first find the enhancement of risk adjusted returns due to risk reduction rather than return increasement for all the portfolios of consideration. Second, the enhancement is more pronounced for the trading strategies using correlations as well as volatilities compared to those using volatilities only. Third, the diversification effect has become stronger after the global financial crisis in 2008. Lastly, we find that the performance of the growth optimal portfolio can be improved by utilizing the well-known momentum phenomenon in stock markets to select the length of the sample period to estimate the expected return. Research implications or Originality - This study shows the potential benefits of adding the U.S. dollar to the portfolios of Korean stocks. The current study is the first to investigate the portfolio of Korean stocks and U.S. dollar from investment perspective.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3417-3426
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• 2012

This study aims to determine how ownership structure (share-holding ratio of insiders, foreigners) affects agent costs (the portion of asset efficiency or non-operating expenses) through empirical analysis. However, as existing studies on correlations between ownership structure and agent costs adopted Pooled OLS Model, this study focused on additionally formulating Fixed Effect Model and Random Effect Model aimed to reflect the time of data formation and corporate effects as study models based on verification results on the suitability of Pooled-OLS Model before comparative analysis for the purpose of improvement of credibility and statistical validity of the results of empirical analysis based on the premise that the Pooled OLS Model is not reliable enough to verify massive panel data. The data has been accumulated over 10 years from 1998 to 2007 after the IMF crisis hit the nation, from a subject 331 companies except for financial institutions. As a result of the empirical analysis, verification of the suitability of model has determined that the Random Effect Model is appropriate in terms of asset efficiency among agent costs items. On the other hand, the Fixed Effect Model is appropriate in terms of non-operating costs. As a result of the empirical analysis according to the appropriate model, no hypothesis adopted in the Pooled OLS Model has been accepted. This suggests that developing an appropriate model is more important than other factors for the purpose of generating statistically significant empirical results by showing that different empirical results are produced according to the type of empirical analysis.

• The Korean Journal of Applied Statistics
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• v.22 no.5
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• pp.995-1005
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• 2009

Conditional correlation between financial time series plays an important role in risk management, asset allocation and portfolio selection and therefore diverse efforts for modeling conditional correlations in multivariate-GARCH processes have been made in last two decades. In particular, CCC (cf. Bollerslev, 1990) and DCC(dynamic conditional correlation, cf. Engle, 2002) models have been commonly used since they are relatively parsimonious in the number of parameters involved. This article is concerned with DCC modeling for multivariate GARCH processes in comparison with CCC specification. Various multivariate financial time series are analysed to illustrate possible advantages of DCC over CCC modeling.

• Journal of the Korean Society of School Health
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• v.31 no.1
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• pp.18-28
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• 2018

Purpose: The purpose of this study was to investigate the factors that influence ego-resilience among adolescents who have experienced abuse by parents in South Korea. Methods: This correlational study used the 4th year cross-sectional data of the seventh-grade middle school students who participated in the Korean Children and Youth Panel Survey (KCYPS) in fourth grade. Data analysis was performed by using SPSS/WIN 23.0 program, which included descriptive statistics, Pearson's correlations coefficient, and hierarchical regression. Results: The results of the hierarchical regression of model 5 revealed that the quality of peer relations played the most significant role in predicting ego-resilience of abused adolescents, followed by self-identity. Also, self-esteem, the quality of teacher-student relationships, excessive expectations from parents, and community awareness had a significant impact on the variance of self-resilience in abused adolescents. This regression model explained 42% of the variance. Conclusion: This study showed that ego-resilience, an asset and resource to help adolescents overcome adverse effects of abuse, was influenced by social environment as well as individual factors. In addition, social support from peers and teachers had greater influence on ego-resilience than support from family members. Thus, the factors identified in this study need to be considered in programs designed to improve ego-resilience as well as in policies for abused adolescents.