Optimal Bond Portfolio for Investors with Long Time Horizons

We study the optimal bond portfolio for an investor with long time horizonusing Japanese interest rate data. A simple one-factor term structure modelis used for our numerical example. The optimal portfolio is computed using thetechnique of stochastic flows and Monte Carlo simulation. The hedgingportfolio is not negligible and the mean variance portfolio is very sensitiveto parameter values. The optimal portfolio is highly leveraged for a typicalparameter value. The investor holds a zero-coupon bond because of the lowerbound restriction on investor's wealth. The lower bound constraint may makethe optimal portfolio more realistic.     

Life-Cycle Portfolio Choice with Additive Habit Formation Preferences and Uninsurable Labor Income Risk

This article explores the implications of additive and endogenoushabit formation preferences in the context of a life-cycle modelof an investor who has stochastic uninsurable labor income.To solve the model, I analytically derive the habit-wealth feasibilityconstraints and show that they depend on the worst possiblepath of future labor income and on the habit strength, but noton the probability of the worst income. When there is only aslim chance of a severe income shock, the model implies muchmore conservative portfolios. The model also predicts that forsome low to moderately wealthy households, the portfolio shareallocated to stocks increases with wealth. Because of this feature,the model can generate more conservative portfolios for youngerthan for middle-aged households. The effects of habits on portfoliochoice are robust to income smoothing through borrowing or flexiblelabor supply. One controversial finding is that for high valuesof the habit strength parameter, usually required for the resolutionof asset pricing puzzles in general equilibrium, the life-cyclemodel predicts counterfactually high wealth accumulation. (JEL:G11, G12)     

Correlation Risk and Optimal Portfolio Choice

We develop a new framework for multivariate intertemporal portfolio choice that allows us to derive optimal portfolio implications for economies in which the degree of correlation across industries, countries, or asset classes is stochastic. Optimal portfolios include distinct hedging components against both stochastic volatility and correlation risk. We find that the hedging demand is typically larger than in univariate models, and it includes an economically significant covariance hedging component, which tends to increase with the persistence of variance–covariance shocks, the strength of leverage effects, the dimension of the investment opportunity set, and the presence of portfolio constraints.     

Optimal Portfolio Choice Under Incomplete Information

Models of asset pricing generally assume that the variables which characterize the state of the economy are observable. However, the distributional properties of asset prices that are relevant for portfolio decisions are in general not observable, and therefore must be estimated. The estimation of expected returns is a particularly difficult problem and estimation errors are likely to be substantial. In this light, it is reasonable to examine whether the assumption of observability of expected returns and other relevant state variables causes significant mis-specification in equilibrium models of asset prices. This paper has three main objectives: first, to derive optimal estimators for the unobservable expected instantaneous returns using observations of past realized returns; second, to establish that estimation and portfolio choice can be solved in two separate steps; third, to analyze the impact of estimation error on investment choices. The estimators of expected returns are in general not consistent, i.e., the estimation error does not tend to disappear asymptotically. The effects of the estimation error, therefore, cannot be ignored even if realized returns are observed continuously over an infinite time period.     

Optimal Portfolio Choice under Heterogeneous Beliefs

This paper analyzes how an investor who is convinced that he can``beat the market' should behave when the equilibrium priceprocess is endogenous. The investor's optimal portfolio is shownto consist of three components: (1) a tangency portfolio, (2) ahedge portfolio against changes in the market's valuation ofsecurities, and (3) a hedging position against changes in thedivergence between the investor's and the market's beliefs. Thesign and magnitude of this third component will depend on investorpreferences and on the divergence in the investor's and themarket's quality of information. A numerical example illustratesthat the effect of heterogeneous beliefs on optimal portfolioallocations can be significant.     

Income Risk and Portfolio Choice: An Empirical Study

This paper investigates the relationship between portfolio choice and labor income risk in the National Longitudinal Survey of Youth 1979 Cohort. Permanent income risk (variability of shocks to income that have permanent effect) significantly reduces the share of risky assets in the household's portfolio, while transitory income risk (variability of shocks with no lasting effect) does not. This result provides strong evidence that households' portfolio choices respond to labor income risks in a manner consistent with economic theory.     

The Effect of Information Quality on Optimal Portfolio Choice

Three types of agents acting on different information sets are considered: fully informed agents, insiders, and outsiders. Differences in information quality are shown to affect the properties of their optimal portfolios. For an outsider, the share of wealth invested in the stock is decreasing in the variance of the stock. However, for an insider, the effect of an increasing stock variance on the optimal portfolio weight is ambiguous. In a calibration to U.S. data, the confidence intervals of the insider's demand for the stock converge, whereas the outsider's confidence intervals become wider.     

Variable Selection for Portfolio Choice

We study asset allocation when the conditional moments of returns are partly predictable. Rather than first model the return distribution and subsequently characterize the portfolio choice, we determine directly the dependence of the optimal portfolio weights on the predictive variables. We combine the predictors into a single index that best captures time variations in investment opportunities. This index helps investors determine which economic variables they should track and, more importantly, in what combination. We consider investors with both expected utility (mean variance and CRRA) and nonexpected utility (ambiguity aversion and prospect theory) objectives and characterize their market timing, horizon effects, and hedging demands.     

Losing Money on Arbitrage: Optimal Dynamic Portfolio Choice in Markets with Arbitrage Opportunities

We derive the optimal investment policy of a risk-averse investorin a market where there is a textbook arbitrage opportunity,but where liabilities must be secured by collateral. We findthat it is often optimal to underinvest in the arbitrage bytaking a smaller position than collateral constraints allow.Even when the optimal policy is followed, the arbitrage portfoliotypically experiences losses before the final convergence date.In fact, its initial performance may be indistinguishable fromthat of a conventional portfolio with a poor track record. Theseresults have important implications for the role of arbitrageursin financial markets.     

劳动收入、财富与资产选择：一个文献综述

本文对国外有关家庭劳动收入与资产选择,财富与资产选择以及在房产和股票上进行的资产选择的有关研究文献进行了综述.一些学者研究认为劳动收入的形成吸引投资者随着年龄的增长减少股票持有的比例,因而提供了在流行的金融文献中理性的建议的证据.一些学者研究认为家庭在股票上的投资的比例随着他们财富的增加而增加.一些学者研究发现富裕的家庭获得更多的信息,因为信息产生增加的回报,因而对股票的需求是财富的凸函数.还有学者研究发现房价风险挤出了股票持有量,这对高的和低的金融净资产投资者都是如此,但是,这种挤出效应在低的金融净价值水平上比较大.这些研究成果对研究我国家庭投资行为有一定的参考和借鉴作用.     

Portfolio Choice over the Life-Cycle when the Stock and Labor Markets Are Cointegrated

We study portfolio choice when labor income and dividends are cointegrated. Economically plausible calibrations suggest young investors should take substantial short positions in the stock market. Because of cointegration the young agent's human capital effectively becomes “stock‐like.” However, for older agents with shorter times‐to‐retirement, cointegration does not have sufficient time to act, and thus their human capital becomes more “bond‐like.” Together, these effects create hump‐shaped life‐cycle portfolio holdings, consistent with empirical observation. These results hold even when asset return predictability is accounted for.     

Optimal Portfolio Selection with Transaction Costs

Abstract

This paper examines the lifetime portfolio-selection problem in the presence of transaction costs. Using a discrete time approach, we develop analytical expressions for the investor's indirect utility function and also for the boundaries of the no-transactions region. The economy consists of a single risky asset and a riskless asset. Transactions in the risky asset incur proportional transaction costs. The investor has a power utility function and is assumed to maximize expected utility of end-of-period wealth. We illustrate the solution procedure in the case in which the returns on the risky asset follow a multiplicative binomial process. Our paper both complements and extends the recent work by Gennotte and Jung (1994), which used numerical approximations to tackle this problem.     

Multivariate Shrinkage for Optimal Portfolio Weights

Abstract

This paper proposes a multivariate shrinkage estimator for the optimal portfolio weights. The estimated classical Markowitz weights are shrunk to the deterministic target portfolio weights. Assuming log asset returns to be i.i.d. Gaussian, explicit solutions are derived for the optimal shrinkage factors. The properties of the estimated shrinkage weights are investigated both analytically and using Monte Carlo simulations. The empirical study compares the competing portfolio selection approaches. Both simulation and empirical studies show that the proposed shrinkage estimator is robust and provides significant gains to the investor compared to benchmark procedures.     

Comonotonic Approximations for Optimal Portfolio Selection Problems

We investigate multiperiod portfolio selection problems in a Black and Scholes type market where a basket of 1 riskfree and m risky securities are traded continuously. We look for the optimal allocation of wealth within the class of “constant mix” portfolios. First, we consider the portfolio selection problem of a decision maker who invests money at predetermined points in time in order to obtain a target capital at the end of the time period under consideration. A second problem concerns a decision maker who invests some amount of money (the initial wealth or provision) in order to be able to fullfil a series of future consumptions or payment obligations. Several optimality criteria and their interpretation within Yaari's dual theory of choice under risk are presented. For both selection problems, we propose accurate approximations based on the concept of comonotonicity, as studied in Dhaene et al. (2002 a,b) . Our analytical approach avoids simulation, and hence reduces the computing effort drastically.     

Dynamic Portfolio Choice with Stochastic Wage and Life Insurance

We study optimal insurance, consumption, and portfolio choice in a framework where a family purchases life insurance to protect the loss of the wage earner's human capital. Explicit solutions are obtained by employing constant absolute risk aversion utility functions. We show that the optimal life insurance purchase is not a monotonic function of the correlation between the wage and the financial market. Meanwhile, the life insurance decision is explicitly affected by the family's risk preferences in general. The model also predicts that a family uses life insurance and investment portfolio choice to hedge stochastic wage risk.     

Optimal Portfolio Selection with Transaction Costs and Finite Horizons

We examine the optimal trading strategy for a CRRA investorwho maximizes the expected utility of wealth on a finite dateand faces transaction costs. Closed-form solutions are obtainedwhen this date is uncertain. We then show a sequence of analyticalsolutions converge to the solution to the problem with a deterministicfinite horizon. Consistent with the common life-cycle investmentadvice, the optimal trading strategy is found to be horizondependent and largely buy and hold. Moreover, it might be optimalfor the investor in our model not to buy any stock, even whenthe risk premium is positive. Further analysis of the optimalpolicy is also provided.     

家庭课税--我国个人所得税课税单位的另一种选择

一国政府可以推行以个人为基础的税收制度,也可以推行以家庭为基础的联合课税制。不同的税收制度会产生不同的公平与效率结果,这也是从课税单位选择角度考察的家庭经济学的一个方面。我国必须从实际出发,在追求公平与效率的最大化目标中选择家庭课税与个人申报纳税并存的纳税单位模式。