• The Journal of Asian Finance, Economics and Business
• /
• v.7 no.12
• /
• pp.1-10
• /
• 2020

This study investigates the problem of outlier detection based on discrete wavelet transform in the context of time series data where the identification and treatment of outliers constitute an important component. An outlier is defined as a data point that deviates so much from the rest of observations within a data sample. In this work we focus on the application of the traditional method suggested by Tukey (1977) for detecting outliers in the closed price series of the Saudi Arabia stock market (Tadawul) between Oct. 2011 and Dec. 2019. The method is applied to the details obtained from the MODWT (Maximal-Overlap Discrete Wavelet Transform) of the original series. The result show that the suggested methodology was successful in detecting all of the outliers in the series. The findings of this study suggest that we can model and forecast the volatility of returns from the reconstructed series without outliers using GARCH models. The estimated GARCH volatility model was compared to other asymmetric GARCH models using standard forecast error metrics. It is found that the performance of the standard GARCH model were as good as that of the gjrGARCH model over the out-of-sample forecasts for returns among other GARCH specifications.

• The Journal of Fisheries Business Administration
• /
• v.41 no.1
• /
• pp.73-91
• /
• 2010

The objective of this study is to examine the hedging effectiveness of shrimp futures market. Hedging effectiveness is measured by OLS model based on rolling windows. Analysis data are obtained from Kansai Commodities Exchange in Osaka and are weekly data of frozen shrimp futures and cash prices in the time period from July 9, 2003, to May 9, 2007. The empirical results are summarized as follows:First, the correlation coefficients between the nearby futures price changes and the cash(16/20) price changes are very low and have range from 0.141 to 0.208 values. Second, the minimum variance hedge ratios($\hat{\beta}$) are all statistically different from 0 at the 5% level and range from 0.0477 to 0.5039 values excluding Indian shrimps(26/30). Ex post hedging effectiveness, as measured by the coefficient of determination, $R^2$, is relatively very low and range from a low of 0.4% for west-south Indian shrimps(26/30) to a high 4.3% for Vietnamese shrimps(16/20). Third, ex ante hedging effectiveness, as measured by out-of-sample hedging period, is also very low and range from a low of -4.4% for west-south Indian shrimps(21/25) to a high of 3.4% for Vietnamese shrimps(16/20). This indicates that the shrimp futures market doesn't behave as risk management instrument of shrimp spot.

• The Korean Journal of Applied Statistics
• /
• v.28 no.4
• /
• pp.703-719
• /
• 2015

We propose an extension of the Lee and Jho (2015) mean reverting the two factor mortality model by incorporating a period-specific cohort effect. We found that the consideration of cohort effect improves the mortality fit of Korea male data above age 65. Parameters are estimated by the weighted least squares method and Metropolis algorithm. We also emphasize that the cohort effect is necessary to choose the base survival index to calculate longevity bond issue price. A key contribution of the article is the proposal and development of a method to calculate the longevity bond price to hedge the longevity risk exposed to Korea National Pension Services.

• Proceedings of the KIEE Conference
• /
• 2000.07a
• /
• pp.400-402
• /
• 2000

This paper presents a game theoretic approach for power transactions analysis in a competitive market. The considered competitive power market is regarded as PooICo model, and the participating players are restricted by only two generating entities for simplicity in this paper. The analysis is performed on the basis of marginal cost based relations of bidding price and bidding generations. That is, we assume that the bidding price of each player is determined by the marginal cost when the bidding generation is pre-determined. This paper models the power transaction as a two player game and analyzes by applying the Nash eauilibrium idea. The generalized game model for power transactions covering constant-sum(especially zero-sum), and nonconstant-sum game is developed in this paper. Also, the analysis for each game model are performed in the case studies. Here, we have defined the payoff of each player as the weighted sum of both player's profits.

• Korea Journal of Hospital Management
• /
• v.18 no.2
• /
• pp.81-103
• /
• 2013

This study is to research cost accounting practice and to analyze propriety of patients' medical payment in artificiality kidney center. The researched cost datum of the year 2012 are as follows. - Hemodialysis medical treatment was reimbursed as much as 158,001 won in case of health insured patients, but payed-off as much as 135,810 won. - The average figure of the total hospitals and clinic center is 1,603,303 won, and one time cost of hemodialysis treatment is 154,487 won. Optimal treatment pay are suggested as follows. First, Regardless of the notified classification from MOHW(Ministry of Health and Welfare), 136,000 won of fixed price payment classification needs to be reclassified by patients, severity and tobe rearranged by fixed price payment system of hospitals. Second, Fixed payment code notified by the Ministry of Health and Welfare is recommended to be simplifies and to reflect according to contents of the medical treatment rendered to patients. Third, Establishment of artificial kidney center has to be risk managed because of its huge investment. Fourth, Cost analysis model has to be maintained as basis together with appropriate application of conversion index model mixed with SGR model.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.19 no.3
• /
• pp.217-232
• /
• 1999

The ability to see the internal organs of the human body in a noninvasive way is a powerful diagnostic tool of modern medicine. Among these imaging modalities such as X-ray, MRI, and ultrasound. MRI and ultrasound are presenting much less risk of undesirable damage of both patient and examiner. In fact, no deleterious effects have been reported as a result of clinical examination by using MRI and ultrasound diagnostic equipment. As a result. their market volume has been rapidly increased. MRI has a good resolution. but there are a few disadvantages such as high price. non-real-time imaging capability. and expensive diagnostic cost. On the other hand, the ultrasound imaging system has inherently poor resolution as compared with X-ray and MRI. In spite of its poor resolution, the ultrasound diagnostic equipment is lower in price and has an ability of real-time imaging as compared with the others. As a result. the ultrasound imaging system has become general and essential modality for imaging the internal organs of human body. In this review various researches and developments to enhance the resolution of the ultrasound images are explained and future trends of the ultrasound imaging technology are described.

• Asia-Pacific Journal of Business
• /
• v.11 no.4
• /
• pp.243-254
• /
• 2020

Purpose - This paper explores whether overnight returns measured from the last closing price to today's opening price explain the cross-section of stock returns. Design/methodology/approach - This study is conducted using the Korean stock market data from 1998 to 2018, obtained from DataGuide database. The analysis begins with portfolio-level tests, followed by firm-level cross-sectional regressions. Findings - First, when decile portfolios sorted on the daily average of overnight returns in the previous months, the highest decile portfolio exhibits a significant negative risk-adjusted return. This suggests that stocks with higher average overnight returns are temporarily overvalued due to buying pressure from investors. Second, at least 6 months of persistence exists in average overnight returns, which is in line with the results reported by Barber, Odean and Zhu (2009) that investor sentiment persists over several weeks. Finally, Fama-MacBeth cross-sectional regression of expected returns after controlling for a variety of firm characteristic variables such as firm size, book-to-market ratio, market beta, momentum, liquidity, short-term reversal, the slope coefficient for overnight returns remains negative and statistically significant. Research implications or Originality - Overall, the evidence consistently suggests that overnight return is considered as a new priced factor in the cross-section of expected returns. The findings of this paper not only adds to finance literature, but also could be useful to practitioners in making stock investment decision.

• Journal of Korea Planning Association
• /
• v.54 no.1
• /
• pp.148-158
• /
• 2019

The purpose of this study is to analyze the impact of earthquake on apartment prices. Many studies have been done analyzing the relationship between natural hazards and residential property prices. Most studies have shown that natural hazards have an negative effect on residential property prices, but some studies have shown that natural hazards have an positive effect on residential property prices. These conflicting analysis result from the lack of considering natural hazard frequency at the analysis site. According to literature reviews risk avoidance tendency are already inherent in prices, thus distorting the relationship between natural hazards and prices. That is, in order to analyze the impact of natural hazards on residential property prices, analysis must be carried out in areas where there has not suffered natural hazard for a long time or where there has been no damage before. Nevertheless, previous studies analyzed areas frequently affected by natural hazards. Gyeongju has been recognized as a safe area from earthquake in the past, an 5.8 magnitude earthquake occurred in September 2016. Analysis results focusing on Gyeongju Earthquake case has shown that the earthquake has affected decrease of apartment prices in hazardous areas, and after earthquake apartment prices have risen over time.

• Asia Marketing Journal
• /
• v.18 no.4
• /
• pp.125-138
• /
• 2017

The goal of the study is to understand how consumers' constraint as opposed to utility structure gives rise to final decision when consumers purchase more than one variant of product at a time, i.e., horizontal variety seeking or multiple-discreteness. Purchase and consumption decision not only produces utility but also involves some sort of cognitive pressure. Past consumption or last purchase is likely to be linked to this burden we face such as concern for obesity, risk of harm, and guilt for mischief. In this research, the existence and the role of dynamic constraint are investigated through a microeconomic utility model with multiple dynamic constraint. The model is applied to the salty snacks data collected from field study where burden for spiciness serves as a constraint. The results are compared to the conventional multiple discreteness choice models of static constraints, and policy implications on price discounts is explored. The major findings are that first, one would underestimate the level of consumer preference for product offerings when ignoring the carry-over of the concern from the past consumption, and second, the impact of price promotion on demand would be properly evaluated when the model allows for the role of constraint as both multiple and dynamic. The current study is different from the existing studies in two ways. First, it captures the effect of 'mental constraint' on demand in formal economic model. Second, unlike the state dependence well documented in the literature, the study proposes the notion of state dependence in different way, via constraint rather than utility.

• Korean Journal of Construction Engineering and Management
• /
• v.18 no.3
• /
• pp.105-116
• /
• 2017

In recent years, large Korean construction companies have suffered serious losses in their overseas business. Many practitioners and researchers have analyzed causes of cost overrun in these projects. However, these arguments have not been empirically verified based on acutal project cases. This study investigated cost overrun rate, contingency, allowance, predicted risk before bidding, and actual and residual risk after award in the 67 international infrastructure projects conducted by 13 large construction companies. The causes of cost overruns are derived as follows. First, they identified the possibility of cost overrun to some extent before the bidding, but did not reflect the enough risk money to bid price. In particular, this behavior was more severe in badly cost-overrun projects. Second, the causes of cost overrun were more influenced by external environmental risk than internal capability risk. However, the internal risk in badly cost-overrun projects was relatively high compared to cost-underrun projects. Third, badly cost-overrun projects failed to mitigate risk. However, cost underrun projects were affected more by low exterior risk conditions than by well mitigated risk. This study provides more informed knowledge in controlling project costs in international infrastructure projects.