Earticle

본 연구는 국내 회사채 시장에서의 모멘텀 현상에 대해 분석하였다. 첫 번째, 회사채 시장에서 모멘텀 현상이 발견되었으며, 이는 기존의 채권과 주식에 대한 체계적인 위험 요인들(Fama and French, 1993, Carhart 1997)로 설명되지 않았다. 두 번째, 모멘텀 전략의 수익성은 주로 평가기간과 보유기간이 6개월 이내로 짧은 경우에 강하게 나타났다. 세 번째, 회사채 모멘텀 전략의 수익성은 금융위기를 제외한 기간과 경기 확장기에서 강하게 나타났다. 네 번째, 회사채 모멘텀 현상은 주로 신용등급이 낮은 그룹에서 강하게 나타났다. 다섯 번째, 모멘텀 현상이 크게 나타나는 신용등급이 낮은 채권 그룹들은 주로 규모가 작고, 유동성이 낮았다. 이러한 결과로 볼 때, 모멘텀 효과가 신용등급이 낮은 쪽에서 발생하는 것은 정보의 지연 반응 효과(Hong and Stein, 1999)에 의한 가능성이 있는 것으로 추측할 수 있다. 여섯 번째, 과거 연구(Gerbhart, Hvidkjaer and Swaminathan, 2005)에서 발견되었던 주식과 채권 모멘텀 간의 전이효과(Spillover)는 나타나지 않았다. 마지막으로 채권의 신용등급이 상향 조정되어 발생하는 수익률의 증가는 모멘텀에 큰 영향을 끼치지 못했다.

The momentum effect is the phenomenon whereby the higher the past return on an asset, the more persistent this return will be in the future. The momentum effect can be found not only in equity, but also in several other asset classes. For example, recent studies show that momentum occurs in the corporate bond market (Pospisil and Zhang, 2010; Jostova et al., 2013; Israel et al. 2017; Houweling and Zundert, 2017, Ho and Wang, 2018). This phenomenon has been documented in the U.S. and various other regions, where various strategies for promoting momentum are appearing. However, empirical studies on the momentum effect in Korea are mostly limited to stocks. AAlthough bonds represent a large proportion of Korea’s financial market, studies of the existence of momentum in this market are still rare. Therefore, we attempt to determine whether the momentum effect exists in the Korean corporate bond market, and if so, what drives this effect. We focus on the corporate bond market, not the government (treasury) bond market, for the following reasons. Depending on the characteristics of the firm that issues a corporate bond, the speed at which investors respond to this information may vary. Given the characteristics of corporate bond issuers, the momentum effect is more likely to occur if there are differences in the speed at which information is reflected. In contrast, in the government bond market, issuers are not diverse. Therefore, the information asymmetry among market participants is smaller for government than corporate bonds, so investors have less influence in the government bond market. Participants in the corporate bond market are more likely to interpret private or public information differently from each other than their counterparts in the government bond market are. Our main results are as follows. First, the higher the past return of a bond, the higher its future return. In other words, we verify the momentum effect. A momentum strategy comprising a six month formation period and a six month holding period shows an average return of 0.17% per month (2.02% per year). The momentum in the corporate bond market is not explained by previously observed systematic risk factors for bonds and stocks (Fama and French, 1993, Carhart 1997). Thus, we cannot conclude that the observed momentum of corporate bonds is associated with compensation for systematic risk. The profitability of the abovementioned corporate bond momentum strategy remains robust even when we control for various characteristics, such as the duration and age of the bond. Second, the profitability of the bond momentum strategy is strong when the formation period and holding period are the short-term periods of three to six months each. The corporate bond momentum is mostly sustained in the short term. Third, the bond momentum strategy is profitable during the period excluding financial crisis and economic expansion, but not during the period including financial crisis and contraction. Fourth, the corporate bond momentum is strong in the low credit rating group. In other words, the higher the past return, the higher the future return in the group of firms with low credit ratings. Fifth, we find that most of the firms in the low credit rating group, which shows a significant momentum effect, are small and have low liquidity. Accordingly, we suggest that the momentum effect occurs at the lower credit level due to the gradual information diffusion phenomenon reported by Hong and Stein (1999). For example, momentum is high under small market capitalization, when private information is difficult to spread. In addition, it is difficult to interpret information from firms with low credit ratings. Sixth, we do not find evidence of the spillover between stock momentum and bond momentum reported in previous studies (Gerbhart, Hvidkjaer, and Swaminathan, 2005). For example, we do not observe a significant relationship between high stock returns in the past and high future bond returns. Finally, after controlling for the effect of bond rating changes on bond returns, the performance of the momentum strategy remains statistically and economically significant. Our study has the following academic and practical implications. First, it reveals a momentum phenomenon in non-stock assets, namely corporate bonds, in the Korean market. Many studies focus on the momentum phenomenon in stock markets. Our results suggest that we also need to research the momentum phenomenon that can occur in various asset classes in Korea. Second, portfolio managers can use our findings to develop an effective bond investment strategy. In the overall asset management industry in Korea, investments in corporate bonds are increasing, especially among institutional investors such as pension funds and insurance companies. Therefore, based on the results of this study, the abovementioned momentum strategy can be used to obtain excess returns in the Korean bond market.

본 연구는 국내 회사채 시장에서 과거 수익률이 높을수록, 미래에도 높은 수익률이 지속되는 모 멘텀 현상이 존재하는지를 밝히고, 어떠한 원인으로 나타나는지를 살펴보았다. 첫 번째, 회사채의 과거 수익률이 높을수록, 향후 수익률이 높은 모멘텀 현상이 발견되는 것으로 나타났다. 그리고 회사채 모멘텀은 기존의 채권과 주식에 대한 체계적인 위험 요인들(Fama and French, 1993, Carhart 1997)로는 설명되지 않았다. 따라서 관측되는 회사채의 모멘텀 현상은 기존에 정의된 위 험에 대한 보상으로 보기는 어려웠다. 두 번째, 모멘텀 전략의 수익성은 주로 평가기간과 보유기 간이 모두 6개월 이내로 짧은 경우에 강하게 나타났다. 세 번째, 회사채 모멘텀 전략의 수익성은 금융위기를 제외한 기간과 경기확장기에서 강하게 나타났으며, 반면 금융위기와 경기 수축기에서 는 나타나지 않았다. 네 번째, 회사채 모멘텀 현상은 주로 신용등급이 낮은 그룹에서 강하게 나타 났다. 다섯 번째, 모멘텀 효과가 크게 나타나는 신용등급이 낮은 채권 그룹들은 주로 규모가 작고, 유동성이 낮았다. 이러한 결과로 볼 때, 모멘텀 효과가 신용등급이 낮은 쪽에서 발생하는 것은 정 보의 지연 반응 효과(Hong and Stein, 1999)에 의한 가능성이 있는 것으로 추측할 수 있다. 마지 막으로, 과거 연구들(Gerbhart, Hvidkjaer and Swaminathan, 2005)에서 발견되었던 주식 모멘텀과 채권 모멘텀 간의 이전효과(Spillover)는 특별하게 나타나지 않았다.

The momentum effect is the phenomenon that the higher the past return of the asset, the more persistent the high return. We can find the momentum effect in not only equity, but also several other asset classes and the U.S. In addition, it is found in various regions, and various kinds of momentum strategies are appearing. In particular, among other assets, recent studies have argued that momentum effects exist in the corporate bond market (Pospisil and Zhang, 2010; Jostova et al., 2013; Israel et al. 2017; Houweling and Zundert, 2017, Ho and Wang, 2018). However, empirical studies on the momentum phenomenon in Korea are mostly limited to stocks. Among other assets, although bonds have a large portion of the domestic financial market, studies on the existence of momentum in the bond market are still difficult to find in Korea. Our results are as follows. First, the higher the past return of the bond, the higher the future past return. In other words, we can verify the momentum effect. The momentum strategy with six months formation periods and six months holding periods shows an average return of 0.27% per month (3.26% per year). And the corporate bond momentum is not explained by the existing systematic risk factors for bonds and stocks (Fama and French, 1993, Carhart 1997). Thus, we cannot conclude that the observed momentum of corporate bonds is associated with compensation for systematic risk. The profitability of the momentum strategy is robust even when we control various characteristics such as duration and the age of bond. Second, the profitability of the bond momentum strategy is strong when the formation period and holding period were short. For example, the profitability of the momentum strategy was significant and high in the short-term period of 3 ~ 6 months formation and holding periods, while the profitability of the momentum strategy deteriorated in 9 ~ 12 months formation and holding periods. As such, the corporate bond momentum is mostly sustained in the short term. Third, the bond momentum strategy is profitable during the period that excluded the financial crisis and the economic expansion, while not during the financial crisis and the contraction. Fourth, the corporate bond momentum is strong in the low credit rating group. In other words, the higher the past return, the higher the future return in the group with the lower credit rating. Fifth, Low credit rating group, which show significant momentum effects, are mostly small and have low liquidity. From these results, we suggest that the momentum effect occurs at the lower credit level due to the gradual information diffusion hypothesis from Hong and Stein (1999). For example, it is found that the momentum is high in the small market capitalization, where private information is difficult to spread. Moreover, it is hard to interpret the information from the low credit rating firm. Finally, we cannot find the spillover between stock momentum and bond momentum found in previous studies (Gerbhart, Hvidkjaer, and Swaminathan, 2005). For example, no significant relationship is observed, such as a high future bond return for companies with high stock returns in the past. This study has academic and practical implications as follows. First, this study shows that there is a momentum phenomenon in other non-stock assets, especially, the Korean corporate bond. Many studies have focused on the momentum phenomenon in stock markets. Our results suggest that we need to research on the momentum phenomenon that can occur in various asset classes in Korea. Second, portfolio managers can use our findings as a bond investment strategy. In overall asset management industry in Korea, investments in corporate bonds are increasing, especially among institutional investors such as pension funds and insurance companies. Therefore, based on the results of this study, it is possible to establish and use the momentum strategy to obtain excess returns in the Korean bond market.

이 논문은 과거의 산업 포트폴리오 수익률이 어떻게 확률추세(stochastic trend)로부터 전체 주식시장과 두 가지 거시경제 변수(경기동행지수와 산업생산)들을 예측할 수 있는 지를 알아보는 데에 초점을 두고 있다. 먼저, 산업들의 포트폴리오 수익률과 전체 주식시장 수익률이 VAR모형을 토대로 볼 경우 Granger 인과관계를 갖고 있는지를 살펴보았다. 이 분석의 결과에서 건설, 금속, 무역, 반도체, 보험, 비금속광물, 서비스, 섬유, 식료, 운수/창고, 유통, 의류, 자동차부풀, 전기전자, 정유, 조선, 종이/목재, 증권, 컴퓨터, 통신, 화학 등 21개 업종은 각 산업별 포트폴리오 수익률이 전체 주식시장 수익률을 수준에서 통계적으로 유의한 영향을 주고 있음을 알 수 있었다. 이들 21개의 산업별 포트폴리오 수익률은 경제적으로도 중요한 의미를 지니고 있다. 즉, 당월(t)의 비금속광물과 정유, 금속 포트폴리오 수익률 등은 다음 월(t+1)의 전체 주식시장 수익률과 음(-)의 상관관계를 갖고 있는 것을 알 수 있었다. 이는 역사적인 데이터를 살펴볼 때, 이들 산업 제품의 가격의 상승은 향후 경제에 악영향을 주기 때문인 것이다. 반면에, 의류 및 무역 등의 경우에는 반대로 이들 산업들의 포트폴리오 수익률이 전체 주식시장 수익률과 양의 상관관계를 나타내 이들 산업들에 있어서 높은 수익률은 향후 경제가 상승국면이 예상됨을 나타내어 주고 있다. 이와 같은 산업별 포트폴리오 수익률과 거시경제변수 간의 높은 상관관계를 토대로 하여 전체 주식시장 수익률 예측을 가능하게 하는 업종 정보(sector information)의 점진적 확산(slow diffusion) 현상이 발생하게 되는 것이다.

I test the hypothesis that the gradual diffusion of information across asset markets leads to cross-asset return predictability in Korea. Using thirty-six industry portfolios and the broad market index as our test assets, I establish several key results. First, a number of industries such as semiconductor, electronics, metal, and petroleum lead the stock market by up to one month. In contrast, the market, which is widely followed, only leads a few industries. Importantly, an industry's ability to lead the market is correlated with its propensity to forecast various indicators of economic activity such as industrial production growth. Consistent with our hypothesis, these findings indicate that the market reacts with a delay to information in industry returns about its fundamentals because information diffuses only gradually across asset markets. Traditional theories of asset pricing assume that investors have unlimited information-processing capacity. However, this assumption does not hold for many traders, even the most sophisticated ones. Many economists recognize that investors are better characterized as being only boundedly rational(see Shiller(2000), Sims(2201)). Even from casual observation, few traders can pay attention to all sources of information much less understand their impact on the prices of assets that they trade. Indeed, a large literature in psychology documents the extent to which even attention is a precious cognitive resource(see, eg., Kahneman(1973), Nisbett and Ross(1980), Fiske and Taylor(1991)). A number of papers have explored the implications of limited information- processing capacity for asset prices. I will review this literature in Section II. For instance, Merton(1987) develops a static model of multiple stocks in which investors only have information about a limited number of stocks and only trade those that they have information about. Related models of limited market participation include brennan(1975) and Allen and Gale(1994). As a result, stocks that are less recognized by investors have a smaller investor base(neglected stocks) and trade at a greater discount because of limited risk sharing. More recently, Hong and Stein(1999) develop a dynamic model of a single asset in which information gradually diffuses across the investment public and investors are unable to perform the rational expectations trick of extracting information from prices. Hong and Stein(1999). My hypothesis is that the gradual diffusion of information across asset markets leads to cross-asset return predictability. This hypothesis relies on two key assumptions. The first is that valuable information that originates in one asset reaches investors in other markets only with a lag, i.e. news travels slowly across markets. The second assumption is that because of limited information-processing capacity, many (though not necessarily all) investors may not pay attention or be able to extract the information from the asset prices of markets that they do not participate in. These two assumptions taken together leads to cross-asset return predictability. My hypothesis would appear to be a very plausible one for a few reasons. To begin with, as pointed out by Merton(1987) and the subsequent literature on segmented markets and limited market participation, few investors trade all assets. Put another way, limited participation is a pervasive feature of financial markets. Indeed, even among equity money managers, there is specialization along industries such as sector or market timing funds. Some reasons for this limited market participation include tax, regulatory or liquidity constraints. More plausibly, investors have to specialize because they have their hands full trying to understand the markets that they do participate in.