Controlling portfolio skewness and kurtosis without directly optimizing third and fourth moments

In spite of their importance, third or higher moments of portfolio returns are often neglected in portfolio construction problems due to the computational difficulties associated with them. In this paper, we propose a new robust mean–variance approach that can control portfolio skewness and kurtosis without imposing higher moment terms. The key idea is that, if the uncertainty sets are properly constructed, robust portfolios based on the worst-case approach within the mean–variance setting favor skewness and penalize kurtosis.     

Measuring and Optimizing Portfolio Credit Risk: A Copula‐based Approach*

In this work, we present a methodology for measuring and optimizing the credit risk of a loan portfolio taking into account the non‐normality of the credit loss distribution. In particular, we aim at modelling accurately joint default events for credit assets. In order to achieve this goal, we build the loss distribution of the loan portfolio by Monte Carlo simulation. The times until default of each obligor in portfolio are simulated following a copula‐based approach. In particular, we study four different types of dependence structure for the credit assets in portfolio: the Gaussian copula, the Student's t‐copula, the grouped t‐copula and the Clayton n‐copula (or Cook–Johnson copula). Our aim is to assess the impact of each type of copula on the value of different portfolio risk measures, such as expected loss, maximum loss, credit value at risk and expected shortfall. In addition, we want to verify whether and how the optimal portfolio composition may change utilizing various types of copula for describing the default dependence structure. In order to optimize portfolio credit risk, we minimize the conditional value at risk, a risk measure both relevant and tractable, by solving a simple linear programming problem subject to the traditional constraints of balance, portfolio expected return and trading. The outcomes, in terms of optimal portfolio compositions, obtained assuming different default dependence structures are compared with each other. The solution of the risk minimization problem may suggest us how to restructure the inefficient loan portfolios in order to obtain their best risk/return profile. In the absence of a developed secondary market for loans, we may follow the investment strategies indicated by the solution vector by utilizing credit default swaps.     

Investment horizon effect on asset allocation between value and growth strategies

How does the optimal risk exposure of assets change as their investment horizons increase? Does this impact investment portfolio decision-making, in particular, optimal asset allocation between value and growth strategies over various investment horizons? This paper adopts a new approach to address these questions by examining portfolio allocation between value and growth stocks over various investment horizons. This new approach is based on wavelet analysis, which decomposes the returns of a particular investment strategy across multiple investment horizons. The key empirical results show that the success of pursuing the value strategy (short-selling growth stocks and going long on value stocks) is impacted by the approach used to classify value and growth stock returns. We explore two common alternatives: Fama-French versus Standard & Poor's (S&P) 500/Barra portfolios. The results using Fama-French portfolios show that as the investment horizon increases, the optimal mean allocation of investors tilts heavily away from growth stocks, particularly for lower and moderate levels of risk aversion. Interestingly, for S&P 500/Barra portfolios the allocation weights between value and growth do not vary much.     

VaR-implied tail-correlation matrices

Empirical evidence suggests that asset returns correlate more strongly in bear markets than conventional correlation estimates imply. We propose a method for determining complete tail-correlation matrices based on Value-at-Risk (VaR) estimates. We demonstrate how to obtain more efficient tail-correlation estimates by use of overidentification strategies and how to guarantee positive semidefiniteness, a property required for valid risk aggregation and Markowitz-type portfolio optimization. An empirical application to a 30-asset universe illustrates the practical applicability and relevance of the approach in portfolio management.     

Incentives and Voluntary Investment in Employer Shares

Using a partial equilibrium model, this paper makes a first attempt to provide an explanation based on rational behaviour for the basic big puzzle of why workers have large holdings of the shares of their employer in their defined contribution (DC) pension plans. The primary explanations in the literature seem to be behavioural ones that involve sub‐optimal behaviour. This paper attempts to see how far a standard optimizing setting in a principal–agent type framework can go in explaining the same phenomenon. It uses an incentive approach involving two agents, senior managers and workers to show how portfolio weights can be voluntarily shifted away from what would be first best in the absence of an incentive problem.     

Multi-objective private wealth allocation without subportfolios

As opposed to institutional investors, individual investors typically have several investment objectives in mind. The traditional utility maximization approach is not only oversimplified but also may not be suitable for real world application. Behavioral asset allocation divides a portfolio into subportfolios, which can cause potential problems. This paper follows the Modern Portfolio Theory and introduces the practical idea of treating some goals as constraints. How this works in practice is illustrated by an example of an individual having three different objectives. This article follows the idea of Chen et al. (2006) and includes life insurance. Consumption is modeled into three parts and accommodates a reasonable basis for calculating life insurance requirements and generally integrates consumption into the investment decision. As a whole, the model provides a customized solution for the environment and complex investment goals of an individual.     

A possibilistic portfolio adjusting model with new added assets

In order to fit changes in financial markets, portfolio managers often need to revise an existing portfolio. This article analyzes the portfolio adjusting problem with new added assets. We propose a possibilistic portfolio adjusting model with transaction costs and bounded constraints on holdings of assets, which can be transformed into a linear programming problem. Both the lower bounds on holdings and the total investment constraints influence the optimal portfolio adjusting strategies. Furthermore, a numerical example of a portfolio adjusting problem is given to illustrate our proposed effective approaches. The numerical results show the case that investors do not need to invest total capital and to hold all assets in the portfolio for some required return levels.     

Risk aversion and allocation to long-term bonds

As risk aversion approaches infinity, the portfolio of an investor with utility over consumption at time T is shown to converge to the portfolio consisting entirely of a bond maturing at time T. Previous work on bond allocation requires a specific model for equities, the term structure, and the investor's utility function. In contrast, the only substantive assumption required for the analysis in this paper is that markets are complete. The result, which holds regardless of the underlying investment opportunities and the utility function, formalizes the “preferred habitat” intuition of Modigliani and Sutch (Amer. Econom. Rev. 56 (1966) 178).     

Investment choices: Indivisible non-marketable assets and suboptimal solutions

Several investment decisions deal with non-marketable assets. Non-marketable assets are available only to one investor and are often indivisible. This has relevant consequences on investor investment opportunities. Adhering to a mean–variance representation of the investment space and considering a non-marketable asset (divisible or not), we derive some possible investment scenarios an investor may face. Furthermore, we show how a limited ability to gather and process information affects investor portfolio choices. Our results define a set of conditions under which the non-marketable asset represents a good investment and show that, under certain assumptions, the efficient frontier exhibits non-linearities and intervals of discontinuity.     

On mean-variance portfolio selection under a hidden Markovian regime-switching model

We study a mean-variance portfolio selection problem under a hidden Markovian regime-switching Black–Scholes–Merton economy. Under this model, the appreciation rate of a risky share is modulated by a continuous-time, finite-state hidden Markov chain whose states represent different states of an economy. We consider the general situation where an economic agent cannot observe the “true” state of the underlying economy and wishes to minimize the variance of the terminal wealth for a fixed level of expected terminal wealth with access only to information about the price processes. By exploiting the separation principle, we discuss the mean-variance portfolio selection problem and the filtering-estimation problem separately. We determine an explicit solution to the mean-variance problem using the stochastic maximum principle so that we do not need the assumption of Markovian controls. We also provide robust estimates of the hidden state of the chain and develop a robust filter-based EM algorithm for online recursive estimates of the unknown parameters in the model. This simplifies the filtering-estimation problem.     

Inducing liquidity in thin financial markets through combined-value trading mechanisms

Asset pricing theory hypothesizes that investors are only interested in portfolios; individual securities are evaluated only in terms of their contribution to portfolio risk and return. Yet, standard financial market design is that of parallel, unconnected markets, whereby investors cannot submit orders in one market conditional on events in others. When markets are thin, this exposes them to substantial execution risk. Fear of ending up with unbalanced portfolios after trading may even keep investors from submitting orders, further eroding liquidity and the ability of markets to equilibrate. The suggested solution is a portfolio trading mechanism referred to as combined-value trading (CVT). Investors are allowed to submit orders for packages of securities and the system matches trades and computes prices by optimally combining portfolio orders in an open book. We study the performance of the CVT mechanism experimentally and compare it to the performance of parallel, unconnected double auctions in experiments with similar parametrization and either a similar number of subjects or substantially thicker markets. We present evidence that our portfolio trading mechanism facilitates equilibration to the extent that the thicker markets do. Inspection of order submission and trade activity reveals that subjects manage to exploit the direct linkages between markets enabled by the CVT system.     

DYNAMIC CORRELATION BETWEEN STOCK RETURNS AND EXCHANGE RATE AND ITS DEPENDENCE ON THE CONDITIONAL VOLATILITIES – THE CASE OF SEVERAL EASTERN EUROPEAN COUNTRIES

The objective of the paper is to determine whether the linkage between stock returns and exchange rates in several Eastern European countries was in accordance with the flow oriented model or the portfolio‐balance approach. The dynamic interdependence between exchange rate and stock returns is determined using the Dynamic Conditional Correlation (DCC) framework. The results pointed to a negative dynamic correlation which is in line with portfolio‐balance approach. Rolling regression revealed that conditional correlation was affected primarily by conditional volatility of currency, while the impact of stock returns volatility was negligible.     

Integrated Risk Management with a Filtered Bootstrap Approach

We present a multi-period risk model to measure portfolio risk that integrates market risk, credit risk and, in a simplified way, liquidity risk. Thus, it overcomes the major limitation currently shared by many risk models that are unable to give a complete picture of all portfolio risks according to a single, coherent framework. The model is based on the Filtered Bootstrap approach; hence, it captures conditional heteroskedasticity, serial correlation and non-normality in the risk factors, that is, most of the features of observed financial time series. Being a simulation risk model, it copes in a natural way with derivatives as it allows the full valuation of the probability density function of the contracts. In addition, it is a suitable and flexible way to generate future scenarios on medium‐term horizons, so this model is particularly appropriate for asset management companies.     

Combining the minimum-variance and equally-weighted portfolios: Can portfolio performance be improved?

It is documented in the literature that due to estimation errors, mean-variance efficient portfolios deliver no higher out-of-sample Sharpe ratios than does the naïve equally-weighted portfolio (EWP). This paper demonstrates how the out-of-sample performance of the minimum-variance portfolio (MVP) can be improved in the presence of estimation errors by combining the MVP and EWP. Our results indicate that an appropriate combination of the MVP and EWP can enhance Sharpe ratios under any scenarios considered, and can also reduce the portfolio risk if short-selling is allowed. However, the combination strategy is not able to generate a lower risk level than the MVP when a short-selling restriction is imposed. We find that the optimal combination coefficient depends on the factors that greatly impact estimation errors in the MVP, including sample size, estimation method, no-short-selling restriction, and length of the out-of-sample period under consideration.     

THE EFFECTS OF THE BANK OF JAPAN'S ZERO INTEREST RATE COMMITMENT AND QUANTITATIVE MONETARY EASING ON THE YIELD CURVE: A MACRO‐FINANCE APPROACH*

This paper empirically investigates the effects of the Bank of Japan's (BOJ) zero interest rate commitment and quantitative monetary easing on the yield curve. Applying a macro‐finance approach, we decompose interest rates into expectations and risk premium components and extract the market's perception of the BOJ's policy stance. We make clear the counterfactual policy without the BOJ's commitment. We find some evidence that the commitment lowered interest rates and mat raising the reserve target may have been perceived as a signal indicating the BOJ's accommodative policy stance. The portfolio rebalancing effect has not been found to be significant.     

Multiplicity in general financial equilibrium with portfolio constraints

This paper explores the role of portfolio constraints in generating multiplicity of equilibrium. We present a simple financial market economy with two goods and two households, households who face constraints on their ability to take unbounded positions in risky stocks. Absent such constraints, equilibrium allocation is unique and is Pareto efficient. With one portfolio constraint in place, the efficient equilibrium is still possible; however, additional inefficient equilibria in which the constraint is binding may emerge. We show further that with portfolio constraints cum incomplete markets, there may be a continuum of equilibria; adding incomplete markets may lead to real indeterminacy.     

A portfolio choice model with utility from anticipation of future consumption and stock market mean reversion

This paper studies a consumption and portfolio choice problem of a long-lived investor who derives pleasure not only from current consumption, but also from the contemplation of future consumption. The model assumes that all effects of future consumption on current well being are assumed to enter through a single variable—namely, the “stock of future consumption”—analogously to habit-formation models. The main implications of the model concern the incentives for savings, and the fundamental sources of risk in financial markets. It is shown that, when the stock market exhibits mean reversion, deriving utility from anticipation of future consumption has a tremendous effect on portfolio choice. In particular, mean allocation to stocks is much lower under the proposed preferences relative to the standard preferences, especially for high risk averse investors.     

Consolidation and commercial bank net interest margins: Evidence from the old and new European Union members and candidate countries

This paper examines the effects of financial reforms on the determinants of commercial bank net interest margin in the banking systems of the new EU member countries and candidate countries by dividing the sample period (1995–2006) into two sub-periods: consolidation period (1995–2000) and post-consolidation period (2001–2006). The paper also compares the new and old EU members to check whether differences with respect to the determinants of net interest margins between these two groups of countries exist within the same time period. The results indicate that size and managerial efficiency are negatively and significantly related to net interest margins in the two sub-periods. Regulators should promote merger and acquisition and market entry in order to increase the scale and efficiency of banks operating in the sector. Exploitation of the scale economies seems to be important in decreasing the interest rate spread in the sampled banking sectors. The results further indicate that all macroeconomic variables are statistically insignificant in the second sub-period, suggesting that differences in macroeconomic fundamentals have decreased among the sampled countries due to the increased convergence process in recent years. As for the comparison of the new and old EU members, the results suggest that the financial and economic convergence between the new and old members has not been completed. Macroeconomic differences within the group and between the groups still exist.     

UNCERTAINTY AVERSION AND PORTFOLIO INERTIA

In stock markets, we often observe portfolio inertia, i.e., a situation in which some stocks are not traded or not priced for a few minutes or longer. This is neither an exceptional situation in which some stock price soars too high to be priced, nor the one where some stock price plummets too much to be traded. By introducing the concept of ‘Knightian uncertainty’, Dow and Werlang (1992) account for the existence of portfolio inertia, which has not been accounted for under the concept of ‘risk’. This paper provides a characterization of the spread between buying and selling prices based on a parameter proposed by Ozaki and Streufert (1999, 2001) that enables us to estimate the attitude towards Knightian uncertainty, and shows that an increase (a decrease) in Knightian uncertainty expands (shrinks) the interval in which an investor never changes her initial position. Furthermore, we analyse the effect of an increase in Knightian uncertainty on portfolio inertia based on Epsilon‐contaminations.     

The possibility of informationally efficient markets

A rational expectations equilibrium with positive demand for financial information does exist under fully revealing asset price—contrary to a wide-held conjecture. Whereas a continuum of investors is inconsistent with fully revealing equilibrium, finitely many investors with average portfolios demand information in equilibrium if they can adjust portfolio size in an additive signal-return model. More information diminishes the expected excess return of a risky asset so that investors who only have a choice of portfolio composition or whose asset endowments strongly differ from the average portfolio are worse off. Under fully revealing price, information market equilibria both with and without information acquisition are Pareto efficient.