본 연구는 평균-분산 모형 및 Black-Litterman 모형을 사용하여 국민연금기금의 효율적 대체투자 포트폴리오 구축방안을 검토하였다. 주요 분석결과는 다음과 같다. 첫째, 전통적 Markowitz의 평균-분산 모형에 따라 과거 평균 수익률을 기대수익률의 대용치로 사용하여 샤프 비율을 극대화시키는 대체투자 포트폴리오의 투자비중을 산출한 결과, 특정 자산에 과도한 투자비중이 집중되는 구석해 문제 및 투입변수의 값에 따라 자산배분 결과가 과도하게 바뀌는 민감도의 문제가 발생하였다. 둘째, 전망결합 기대 수익률을 사용하여 투자비중을 산출한 결과, Black-Litterman 모형은 구석해 문제 및 투입변수의 민감성 문제를 완화하면서 동시에 매니저의 시장전망을 반영할 수 있어서 대체투자 포트폴리오 매니저가 실제 자산배분에 사용하기에 유용한 모형임을 확인할 수 있었다. 단, Black-Litterman 모형은 포트폴리오 매니저의 주관적 관점에 따라 자산배분 결과가 상이하게 나타나므로 대체투자 포트폴리오 매니저는 시장전망의 정확성을 제고하는 것이 동 모형을 사용하기 위한 전제 조건이 되어야 할 것이다. 셋째, 시장전망의 정확도가 높고, 적절한 투자비중의 제한이 설정되어 있는 경우 기존 국민 연금의 대체투자대상에 포함되지 못했던 상품자산과 헤지펀드를 대체투자 포트폴리오에 편입시켜 새로운 포트폴리오를 구성하는 것이 대체투자 포트폴리오의 효율성을 향상 시킬 수 있음을 확인하였다. 본 연구는 그 동안 주로 Markowitz의 평균-분산 모형 위주로 6개의 자산군에 자산배분을 해 온 국민연금 기금운용에 운용기관의 전망치를 반영하는 Black-Litterman 모형 및 자산군 확장의 유효성을 실증분석을 통해 제시 하였다. 이를 통해 향후 국민연금의 대체투자 자산배분 전략의 다양화 및 수익률 제고에 기여한다는 면에서 실무적 연구로서의 의의가 있다.
The assets under management (AUM) of the Korean National Pension Fund (NPF), which started from 530 billion won in 1988, reached 426.9 trillion won by the end of 2013. This is the fourth largest pension fund in the world. Over 99% of the Korean NPF portfolio is comprised of finance sector holdings and the NPF’s performance thus depends on the management of financial sector investments. For many years, major investment vehicles in the NPF portfolio have been domestic bonds, domestic stocks, foreign bonds, and foreign stocks.
Recently, alternative investments have become important parts of pension portfolio management. It is common to find alternative investment products such as real estate, infrastructure, private equity, commodities, and hedge funds in various sovereign pension portfolios. As alternative asset classes have little correlation with traditional investments, they help to diversify portfolio risk and also extend portfolios’ efficient frontier. In consequence, the proportion of alternative investments among global pension funds increased from approximately 7% in 2003 to 17% in 2012. The Korean NPF has followed this trend. The amount and proportion of alternative investments in the NPF portfolio steadily increased to reach 40 trillion won and to account for 9.4% of the total portfolio as of the end of 2013. However, few studies have been conducted on the management and performance of alternative investments in Korea.
This study explores a way to construct the optimal alternative investment portfolio for the Korean NPF using both the Markowitz mean-variance and Black-Litterman models. With six asset classes, we use a proxy for the fund’s alternative investment portfolio to test which of the two optimization models is more appropriate for improving portfolio performance. We also construct an alternative investment portfolio with eight asset classes, adding commodity and hedge funds, which are currently excluded from the Korean NPF portfolio, to examine whether including these can enhance the portfolio’s efficiency.
The main results of this study are as follows. First, we construct the optimal alternative investment portfolio with the Markowitz mean-variance model using the historical average returns of various alternative investment assets as proxy for the equilibrium expected returns. However, the model is extremely sensitive to changes in the input variables and often converges to the corner solution, which allocates unreasonably high weights to one or two assets. This reduces the advantages of portfolio diversification. Second, the Black-Litterman model has been devised to improve these limitations of the mean-variance model. It combines the equilibrium expected returns embedded in a market portfolio with managers’ views on its future asset performance. The model alleviates the extreme asset allocation problem. Thus, we suggest that the Black-Litterman model can be more appropriate so long as managers have market- forecasting capabilities. Finally, we confirm that including commodity and hedge funds in the Korean NPF alternative investment portfolio can improve its efficiency, as long as the fund has appropriate market-forecasting capabilities and imposes reasonable portfolio weights restrictions in asset classes.
We consider the Black-Litterman model, which reflects managers’ views on future performance, in preference to the mean-variance model. We provide new insights into asset allocation methodology for the Korean NPF, which has mainly conducted asset allocation using a Markowitz-type mean-variance model. Some of the current alternative investment segment benchmarks used in the Korean NPF do not explain the variance and covariance of their asset classes, and we propose new benchmarks to replace them. Considering the growing prominence of the alternative investment portfolio in the Korean NPF, we suggest that continuous research effort should be made in this area to further improve the performance of the fund.