• The Korean Journal of Applied Statistics
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• v.34 no.1
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• pp.39-56
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• 2021

Many researches have been done on portfolio optimization since Markowitz (1952) published a diversified investment model. Markowitz's mean-variance portfolio optimization problem is established under the assumption that the distribution of returns follows a normal distribution. However, in real life, the distribution of returns does not follow a normal distribution, and variance is not a robust statistic as it is heavily influenced by outliers. To overcome these potential issues, mean-shortfall portfolio model was proposed that utilized downside risk, shortfall, as a risk index. In this paper, we propose a perturbation method that uses the shortfall as a risk index of the portfolio. The proposed portfolio utilizes an adaptive Lasso to obtain a sparse and stable asset selection because it can reduce management and transaction costs. The proposed optimization is easily applicable as it can be computed using an efficient linear programming. In our real data analysis, we show the validity of the proposed perturbation method.

• The Korean Journal of Applied Statistics
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• v.35 no.2
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• pp.229-250
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• 2022

Since the publication of Markowitz's (1952) mean-variance portfolio model, research on portfolio optimization has been conducted in many fields. The existing mean-variance portfolio model forms a nonlinear convex problem. Applying Dantzig's linear programming method, it was converted to a linear form, which can effectively reduce the algorithm computation time. In this paper, we proposed a Dantzig perturbation portfolio model that can reduce management costs and transaction costs by constructing a portfolio with stable and small (sparse) assets. The average return and risk were adjusted according to the purpose by applying a perturbation method in which a certain part is invested in the existing benchmark and the rest is invested in the assets proposed as a portfolio optimization model. For a covariance estimation, we proposed a Gaussian kernel weight covariance that considers time-dependent weights by reflecting time-series data characteristics. The performance of the proposed model was evaluated by comparing it with the benchmark portfolio with 5 real data sets. Empirical results show that the proposed portfolios provide higher expected returns or lower risks than the benchmark. Further, sparse and stable asset selection was obtained in the proposed portfolios.

• The Korean Journal of Financial Management
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• v.15 no.1
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• pp.1-30
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• 1998

본(本) 연구(硏究)는 한국증권시장에서 대표적 대용시장(代用市場)포트폴리오인 한국종합주가지수(韓國綜合株價指數)와 동일가중지수(同一加重指數)의 효율성에 대한 검증을 Hansen(1982)의 다변량의 GMM에 의하여 실시하고자 하였다. 이를 위하여 먼저, 주식수익률자료(株式收益率資料)에 근거한 산업별(産業別)포트폴리오수익률과 초과시장수익률모형(超過市場收益率模型)의 오차항(誤差項)이 정규분포(正規分布)를 벗어남을 증명함으로써 GMM검증방법(檢證方法)의 정당성을 찾고자 하였다. 정규분포에 대한 검증방법(檢證方法)으로서 왜도와 첨도의 검증과 이를 결합한 Jarque-Bera(1980)검증(檢證)을 실시하였다. 둘째로, Hansen(1982)의 GMM을 대용시장(代用市場)포트폴리오의 효율성(效率性) 검증(檢證)에 적용하는 방법에 대한 연구들인 Mackinlay-Richardson(1991), Harvey-Zhou(1993)와 Campbell-Lo-Mackilay(1997) 등을 기초로하여 이들의 방법론을 개선한 3가지의 효율성(效率性) 검증방법(檢證方法)을 제시하였다. 셋째로, 이상의 검증방법(檢證方法)들을 토대로 1980년 1월부터 1997년 6월까지 월별주식수익률(月別株式收益率)의 자료(資料)를 11업종으로 분류하여 산업별(産業別)포트폴리오수익률(收益率)과 초과시장수익률모형(超過市場收益率模型)에 의한 오차항(誤差項)이 정규분포(正規分布)를 따르는지와 아울러 대용시장(代用市場)포트폴리오의 효율성을 검증하였다. 검증결과(檢證結果), 산업별(産業別)포트폴리오수익률과 오차항(誤差項)은 대부분 정규성이 기각(棄却)되어 GMM검증방법(檢證方法)의 정당성이 입증되었다. 따라서 GMM에 의한 효율성(效率性)을 검증한 결과, 한국종합주가지수(韓國綜合株價指數)의 경우에는 평균-분산(平均-分散)프론티어(mean-variance frontier)상(上)에서의 대용시장(代用市場)포트폴리오의 효율성(效率性)은 기각(棄却) 할 수 없는 것으로 나타났으나 평균수익률(平均收益率)이 GMVP의 수익률보다 낮았기 때문에 효율적(效率的) 프론티어(efficient frontier)상(上)의 대용시장(代用市場)포트폴리오의 효율성(效率性)은 기각(棄却)되어 대용시장지수로서의 문제점이 있는 것으로 나타났다. 그러나 동일가중지수(同一加重指數)는 평균수익률이 GMVP의 수익률보다 높을 뿐만아니라 효율적(效率的) 프론티어상(上)의 대용시장(代用市場)포트폴리오의 효율성(效率性)도 채택되어 한국종합주가지수(韓國綜合株價指數)보다 우월한 지수(指數)인 것으로 나타났다.

• Journal of the Korean Data and Information Science Society
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• v.26 no.6
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• pp.1479-1494
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• 2015

Since the Markowitz's mean-variance framework for portfolio analysis, the topic of portfolio optimization has been an important topic in finance. Traditional approaches focus on maximizing the expected return of the portfolio while minimizing its variance, assuming that risky asset returns are normally distributed. The normality assumption however has widely been criticized as actual stock price distributions exhibit much heavier tails as well as asymmetry. To this extent, in this paper we employ the genetic algorithm to find the optimal portfolio under the Value-at-Risk (VaR) constraint, where the tail of risky assets are modeled with the generalized Pareto distribution (GPD), the standard distribution for exceedances in extreme value theory. An empirical study using Korean stock prices shows that the performance of the proposed method is efficient and better than alternative methods.

• Journal of the Korean Data and Information Science Society
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• v.26 no.2
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• pp.323-334
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• 2015

he current VaR model based on the J.P. Morgan's RiskMetrics structurally can not reflect the future economic situation. In this study, we propose a One-factor model resulting from the Wiener stochastic process decomposed into a systematic risk factor and an idiosyncratic risk factor. Therefore, we are able to perform a preemptive risk management by means of reflecting the predicted common risk factors in the model. Stocks in the portfolio are satisfied with the independence to each other because the common factors are fixed by the predicted value. Therefore, we can easily determine the investment in each stock to minimize the variance of the portfolio. In addition, the portfolio VaR is decomposed into the sum of the individual VaR. So we can effectively implement the constitution of the portfolio to meet the target maximum losses.

• Korean Journal of Construction Engineering and Management
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• v.14 no.1
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• pp.23-31
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• 2013

Following the U.S sub-prime mortgage crisis and a slump in properties market, the probability is rising that housing investment would not yield high profit as it used to do until early 2000s. For this reason, the nature of properties market is undergoing a change from a source of lucrative investment to a source of a relatively low but stable profit, such as profit-oriented real estate. This trend is likely to promote REITs market, which is a leading product for indirect investment. Until now, the REITs market has been growing slowly compared to a general housing market or financial markets. However, as the importance of risk management based on portfolio theories increases, stable profit generation of REITs can be effective in risk management. This study conducts an empirical analysis on how investment risks can be diversified by including REITs-a source of relatively stable profit in the equity market-in investment portfolio. The analysis results showed that, similar to food and beverage stocks of highly defensive nature, REITs has a relatively weak correlation with KOSPI that reflects the overall market performance. It also showed very low standard deviation in case of minimum variance portfolio. This suggests that including REITs in investment portfolio can be as effective as including food and beverage stocks for risk diversification. Due to uncertainties, investment always accompanies risks, and balancing potential profits and risks is essential.

• Journal of the Korea Convergence Society
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• v.10 no.9
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• pp.199-207
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• 2019

This study aims to analyze the profitability of Robo-Advisors portfolio combined with the analysts' forecasts on the Korean stock prices. Sample stocks are 8 blue-chips and sample period is from 2003 to 2019. Robo-Advisor portfolio was suggested using the Black-Litterman model combined with the analysts' forecasts and its profitability was analyzed. Empirical result showed the suggested Robo-Advisor algorithm produced 1% annual excess return more than that of the benchmark. The study documented that the analysts' forecasts had an economic value when applied in the Robo-Advisor portfolio despite the prevalent blames from investors. The profitability on small or medium-sized stocks will need to be analyzed in the Robo-Advisor context because their information is relatively less known to investors and as such is expected to be strongly influenced by the analysts' forecasts.

• Journal of Cadastre & Land InformatiX
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• v.49 no.1
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• pp.45-63
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• 2019

Until recently, most people have invested in a traditional portfolio consisting of stocks, bonds and real estates based on the three-division method of properties in Korea. However, this study analyzed the impact of the composition of a portfolio combining representative real estate indirect investment products such as Reits and real estate funds on the investment performance. For this purpose, the empirical analysis using the mean variance model, which is the most appropriate method for the portfolio composition, was used. For variables used in this study, mixed asset portfolios were classified into Portfolio A through Portfolio G depending on the composition of assets, and the price indices selected as Kospi, Krx bond, Reits Trus Y7, Hanwha-Lasal fund, and Office (Seoul). The results are as follows; first Portfolio D, which combined bonds, stocks, Reits and Real Estate funds, and Portfolio G, which added the office, the actual real estate, were shown to have the lowest risk. second, Portfolio B composed of bonds, stocks and Reits and Portfolio D with added real estate funds had the lowest risk while Portfolio F composed of bonds, stocks, offices and real estate funds, and Portfolio G with added Reits were the most profitable. As a result, it has been analyzed that it was more effective to compose a portfolio including Reits and real estate funds, which were real estate indirect investment products that eliminated the illiquidity limitation of real estates than real estates, the traditional three-division method of properties. Therefore, it is possible to minimize the risk of investors and reduce the cost of ownership of the real estate by solving the illiquidity problem that is the biggest disadvantage of the direct investment, In addition, it is considered that it is more necessary to reinvigorate the real estate indirect investment market where small amounts can be invested.

• The Korean Journal of Financial Management
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• v.19 no.1
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• pp.1-32
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• 2002

한국 종합주가지수는 한국증권거래소에 상장된 모든 기업들의 가치 가중치에 의한 포트폴리오의 가격의 시계열이라고 할 수 있다. 따라서 이 지수는 한국 경제의 현재의 활동과 미래의 활동에 대한 예상의 총합의 반영 또는 표상을 표현하는 정보라 할 수 있다. 본 논문에서는 시차변수가 독립변수로 도입될 수도 있으며, 시차변수가 아닌 변수가 독립변수로 도입되는 것이 허용되는 회귀모형을 통하여 구조변화의 회수와 구조변환점을 검정할 수 있는 통계량과 이 통계량의 확률분포를 분석하고 한국 종합주가지수에 적용하여 한국 종합주가 지수의 일별수익률에 구조변화가 발생하였는지의 여부와 발생했다면 발생회수와 변환점들을 발견하는데 그 목적이 있다. 한국 종합주가지수의 일별수익률은 분산의 변화 그리고 평균 및 분산의 동시변화가 1997년 9월 27일에 발생하였다. 자기회귀모형에 의할 때 증권시장의 구조변화는 1999년 11월 16일에 이루어졌다. 평균과 분산의 변화가 일어나 구조변화의 단계를 시작하고 구조변화에 알맞는 환경조성에 2년이 소요된 후에 1999년 11월 16일에 구조변화가 정착되었다. 정착이 이루어진 후에야 비로서 이 두 기간은 서로 다른 경제구조와 증권시장구조가 이루어지고 이에 입각하여 시장의 새로운 운동법칙이 전개되고 있다고 할 수 있을 것이다.

• International Commerce and Information Review
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• v.3 no.2
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• pp.1-16
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• 2001

This study discusses some theoretical implications for efficient utilization of the global E-commerce in a world of uncertainty by beginning with measures of risk and return for the global E-commerce, and by moving to risk and return for a efficient transaction portfolio of many risky methods of transaction. Decision rules are developed to show how individuals choose optimal transaction portfolios that maximize their expected utility of wealth. First, the individuals will generally want to allocate positive amount to the global E-commerce, which requires that the expected marginal utility of wealth equals zero. Secondly, the optimal transaction portfolio will be determined by finding the point of tangency between the efficient trading line and the hightest indifference curve in the mean-variance plane. Thirdly, if the global E-commerce is positively correlated with wealth, it must have an expected return that is higher than the risk-free transaction methods in order to compensate for its risk. Fourthly, on the other hand, if the global E-commerce is negatively correlated with wealth, it will have an expected return that is less than the risk-free transaction methods. Finally, the valuation of global E-commerce depends on the degree of individual's risk aversion and the covariance between the expected return of total wealth and the return of global E-commerce.