Suboptimal international equity portfolio diversification and stock market development

Review of Quantitative Finance and Accounting - This paper examines whether the widely reported phenomena of home and foreign biases (i.e. suboptimal international equity portfolio diversification)...     

The impact of portfolio diversification on mean reverting components of stock indices

Positive autocorrelations are introduced into stock index portfolios when they are formed from individual stock indices while negative autocorrelations are induced in returns by increasing the investment horizon. Using monthly data of six international stock indices, this paper examines the diversification effect with different investment horizons on autocorrelations of stock index portfolios. The results show that portfolio diversification does not alter the impact of the investment horizon on autocorrelations. Different investment horizons, however, have great impact on the diversification effect on autocorrelations. With short (long) horizons, the average autocorrelation coefficient increases (decreases) with an increase in the portfolio size, suggesting that mean-reverting component dominates the delayed adjustment effect in long horizons and vice versa in short horizons. Our results are robust across two 10-year sub-periods.The author would like to thank an anonymous referee of this Journal for the comments on an earlier version of this paper and the Research Committee of Hong Kong Baptist University for the financial support in this research.     

Large returns,conditional correlation and portfolio diversification: a value-at-risk approach

This paper, using daily returns on 30 Dow Jones Industrial stocks for the period 1991-1999, investigates the possibility of portfolio diversification when there are negative large movements in the stock returns (i.e. when the market is bearish). We estimate the quantiles of stock return distributions using non-parametric and parametric methods that are widely being used in measuring value-at-risk (VaR). We find that the average conditional correlation of 30 stocks is much higher when the large movements are negative than that when the market is 'usual'. Further, we find that, contrary to the results of previous studies, there is no notable difference between the average conditional correlations when the large movements are positive and when the market is 'usual'. Moreover, it is evident from the results of the conditional CAPM that the portfolio's diversifiable and non-diversifiable risks, as measured by the error variance of the CAPM and beta respectively, are highly unstable when the market is bearish than that when it is 'usual' or bullish. The overall results suggest that the possibility of portfolio diversification would be eroded when the stock market is bearish. These findings have implications for portfolio diversification and risk management in particular and for finance in general. The ideas presented in this paper can be utilized for testing contagion in the international financial markets, a much-researched topic in international finance.     

Financial literacy and portfolio diversification

We use a survey of individual investors disclosed by the Portuguese Securities Commission (CMVM) in May 2005 to study the impact of investors’ levels of financial literacy on portfolio diversification. We consider distinct aspects of financial literacy, and control for socioeconomic and behavioral differences among individual groups of investors. Our results suggest that investors’ educational levels and their financial knowledge have a positive impact on investor diversification. The information sources used by retail investors to gather information on markets and financial products also have a significant impact on the number of different assets included in a portfolio.     

An international analysis of REITs and stock portfolio management based on dynamic conditional correlation models

This paper analyzes the volatility spillovers and asymmetry between REITs and stock prices for nine countries (Australia, Belgium, Germany, Italy, Japan, The Netherlands, Singapore, the United Kingdom, and the United States) using eight different multivariate GARCH models. We also analyze the optimal weights, hedging effectiveness, and hedge ratios for REIT-stock portfolio holdings with respect to the results. The empirical results indicate that dynamic conditional correlation (DCC) models provide a better fit than the constant conditional correlation models. The DCC with volatility spillovers and asymmetry (DCC-SA) model provides a better fit than the other multivariate GARCH models. The DCC-SA model also provides the best hedging effectiveness for all pairs of REIT-stock assets. More importantly, this result holds for all cases and for all models that we consider, which means that by taking spillover and asymmetry into consideration, hedging effectiveness can be vastly improved.     

Is gold good for portfolio diversification? A stochastic dominance analysis of the Paris stock exchange

This paper aims to assess the role of gold quoted in Paris in the diversification of French portfolios from 1949 to 2012 using the stochastic dominance (SD) approach. The principal advantage of this method is that there is no restriction on the distribution of the returns. Our results show that stock portfolios including gold stochastically dominate those without gold at the second and third orders. This implies that risk-averse investors would be better off by including gold in their stock portfolios to maximize their expected utilities. The study on sub-periods shows that this result holds especially in unstable or crisis times. However, these results do not hold for bond or risk-free portfolios, for which the portfolios without gold dominate those with gold. To check the robustness of our results, our SD analysis of a mixed portfolio (50% stocks, 30% bonds and 20% the risk-free asset) provides results similar to those for portfolios with stocks only, except from 1971 to 1983. Portfolios including gold quoted in London show results similar to those from Paris. The results of mean–variance performance measures confirm the findings of previous studies that gold is good for the diversification of stock portfolios but not for bond portfolios.     

Managerial personal diversification and portfolio equity incentives

This paper examines the diversification choices of top managers and their implications for the levels of portfolio equity incentives as well as for firms' financial policies. Standard portfolio theory should also apply to corporate managers and therefore excessive risk exposures to the firm should create portfolio diversification incentives for the managers. We use a unique dataset from the Taiwan tax data center and construct the measures of the degree of diversification in a manager's equity portfolio that is made up of equities of other firms to capture his motives for diversifying his risk exposure to his own firm. We provide empirical evidence supporting the view that managers have a risk-reduction motive when they trade in the equities of other firms besides their own. Moreover, we document evidence that the degree of diversification in such equity portfolios also significantly affects managerial equity incentives as well as firms' financial policies. Overall, our findings confirm that managers' personal diversification can help make up for the diversification that the managers would otherwise have lost, thereby reducing the agency cost of equity incentive contracts.     

Worst case portfolio vectors and diversification effects

We consider the problem of identifying the worst case dependence structure of a portfolio X ₁,…,X _n of d-dimensional risks, which yields the largest risk of the joint portfolio. Based on a recent characterization result of law invariant convex risk measures, the worst case portfolio structure is identified as a μ-comonotone risk vector for some worst case scenario measure μ. It turns out that typically there will be a diversification effect even in worst case situations. The only exceptions arise when risks are measured by translated max correlation risk measures. We determine the worst case portfolio structure and the worst case diversification effect in several classes of examples as, e.g. in elliptical, Euclidean spherical, and Archimedean type distribution classes.     

Expected stock returns,common idiosyncratic volatility and average idiosyncratic correlation

Motivated by Herskovic et al. (2016), we examine the role of the average idiosyncratic correlation (ICOR) in two types of markets: an emerging market and a developed market. Examining daily stock data from the Chinese stock market for the period 1995 to 2020 and from the US for the period 1926 to 2019, we adopt high-dimensional principal component analysis (PCA) and thresholding methods to re-estimate ICOR. We find that ICOR plays an important role in explaining the expected stock returns, as the common idiosyncratic volatility (CIV) does in Herskovic et al. (2016). ICOR has been neglected in the literature due to large estimation error in the idiosyncratic covariance matrix and our analysis provides evidence that ICOR is nonnegligible in both markets when we control for several common market factors. We show that the average idiosyncratic covariance, which is the numerator of ICOR, exhibits the same pattern as CIV. Furthermore, our regression analyses of expected stock returns in response to ICOR change in both markets show that, in contrast to the negative result for CIV, the stocks’ high risk exposure to ICOR change comes with a higher risk premium, perhaps because of the synchronized but disproportionate changes in the monthly idiosyncratic covariance and idiosyncratic volatility.     

International portfolio diversification and multilateral effects of correlations

Not only are investors biased toward home assets, but when they do invest abroad, they appear to favor countries with returns more correlated with home assets. Often attributed to a preference for familiarity, this ‘correlation puzzle’ further reduces effective diversification. We use a multi-country general equilibrium model of portfolio choice to study how bilateral equity holdings are affected by return correlations among alternative destination and source countries. From the theoretical model, we develop an empirical approach to estimate a gravity equation for equity holdings that incorporates the overall covariance structure in a theoretically rigorous yet tractable manner. Estimation using this approach resolves the correlation puzzle, and finds that international investors do seek the diversification benefits of low cross-country correlations, as theory would predict.     

Sources of gains from international portfolio diversification

This paper looks at the determinants of country and industry specific factors in international portfolio returns using a sample of forty eight countries and thirty nine industries over the last three decades. Country factors have remained relatively stable over the sample period while industry factors have significantly increased during the last decade and dropped again since 2000. The importance of industry and country factors is correlated with measures of economic and financial international integration and development. We find that financial market globalization is the main driving force behind the changes in relative magnitude of the different shocks. Country factors are smaller for countries integrated in world financial markets and have declined as the degree of financial integration and the number of countries pursuing financial liberalization has increased. Higher international financial integration within an industry increases the importance of industry factors in explaining returns. Economic integration of production also helps in explaining returns. Countries with a more specialized production activity have higher country shocks.     

International portfolio diversification and the home bias puzzle

We review the literature on equity home bias, a phenomenon stating that investors do not hold enough foreign equities for an optimally diversified portfolio. We begin by defining the home bias measurement and reviewing related evidence on the bias. Further, we consider four explanations for this puzzling phenomenon: barriers to foreign investment, country-specific risks, information asymmetry, and cultural and behavioral factors. We analyze the related theoretical arguments and empirical findings of prior studies within each explanation. Based on the discussion of previous studies, several avenues for future research are suggested. (JEL G11, G15, F41)     

Transition to the Euro and its impact on country portfolio diversification

By examining the impact of the introduction of the Euro on stock markets and on country diversification within the Eurozone, the evidence does not suggest a high risk to the stock market to justify a risk premium as a result of currency union. Although the Euro market integration has increased inter-country correlations, it does not preclude gains from international diversification, which partially rely on the non-Eurozone countries for an optimal portfolio in a mean-variance framework. Furthermore, the empirical evidence supports that there is a significant stationarity of average correlations over time between pre-Euro and post-Euro periods, and it has improved since the introduction of the Euro. Also, results show that the Euro produced a change in volatility with a different pace within the Eurozone vis-à-vis non-Eurozone countries, to support a direct and opposite relationship between volatility and correlation.     

The effect of limited information and estimation risk on optimal portfolio diversification

This paper analyzes the optimal portfolio choice problem when security returns have a joint multivariate normal distribution with unknown parameters. For the case of limited, but sufficient (sample plus prior) information, we show that for a general family of conjugate priors, the optimal portfolio choice is obtained by the use of a mean-variance analysis that differs from traditional mean-variance analysis due to estimation risk. We also consider two illustrative cases of insufficient sample information and minimal prior information and show that in these cases it is asymptotically optimal for an investor to limit diversification to a subset of the securities. These theoretical results corroborate observed investor behavior in capital markets.     

Financial education,investor protection and international portfolio diversification

This paper investigates the effect of financial education on foreign portfolio investment. We show that higher investor financial education fosters international diversification, and that its role is particularly pronounced where information problems and monitoring costs are likely to be more severe, that is, in countries where protection of minority shareholders' rights is weaker.We interpret this evidence as supportive of the conjecture that financial education lessens the informational constraints binding foreign investors.     

International portfolio diversification: a synthesis and an update

This paper provides a synthesis of the existing literature on international portfolio diversification and presents some new results on the subject. We address the question of whether international portfolio diversification is always a reasonable method of reducing the risk of an investment portfolio without negatively affecting its return expectations. Unfortunately, there is still not a simple answer to this question. When ex-post data is examined, potential benefits of international diversification can certainly be detected. However, we also argue that it might be difficult for investors to select an optimal investment strategy ex-ante, when the correlation structure among the international equity is unstable over time. While such findings do not completely rule out the potential benefits of international diversification, they certainly make them more difficult to realize in practice.     

Global portfolio investment network and stock market comovement

This paper examines the impact of financial connectedness of countries on international stock market comovement. In recent decades, cross-border capital flows have increased dramatically, and I use bilateral cross-border portfolio holdings to create a global portfolio investment network. Using network analysis, I examine the effect of a country's centrality within this network on stock market comovement while also controlling for the country's trade connectedness. The results show that stock markets of countries that occupy highly central positions within the global portfolio investment network exhibit higher comovement after I control for the level of trade connectedness. Countries that simultaneously occupy highly central positions in both financial and trade networks display even higher levels of stock market comovement. Moreover, linkages derived from total portfolio holdings matter just as much as or more than those derived only from equity linkages.     

The effect of the Euro on country versus industry portfolio diversification

We examine the relative benefits of industrial versus geographical diversification in the Euro zone before and after the introduction of the common currency. A priori, one may expect that increased stock market correlation would precipitate a move from geographical towards industrial diversification. We employ the empirical model of Heston and Rouwenhorst but show that adopting a panel data approach is a more efficient estimation method. We find evidence of a shift in factor importance; from country to industry. However, this is not exclusive to the Euro zone but is also present for non-EMU European countries. Therefore, fund managers should pursue industrial rather than geographical diversification strategies.     

Exploring the benefits of international government bond portfolio diversification strategies

We use the Bayesian approach of Wang (1998) to examine the diversification benefits of investing in international government bonds. We find that no short-selling constraints substantially reduce but do not eliminate the diversification benefits when only investing in G7 government bonds with different maturities. There are significant diversification benefits when using the G7 bonds, an inflation-linked bond index, and emerging market bonds even in the presence of no short-selling constraints. The superior performance is driven by the emerging markets bonds. We also find that the diversification benefits vary across different economic states.