The Role of Learning in Dynamic Portfolio Decisions

This paper analyzes the effect of uncertainty about the mean return on the risky asset on the portfolio decisions of an investor who has a long investment horizon. Building on the earlier work of Detemple (1986), Dothan and Feldman (1986), and Gennotte (1986), it is shown that the possibility of future learning about the mean return on the risky asset induces the investor to take a larger or smaller position in the risky asset than she would if there were no learning, the direction of the effect depending on whether the investor is more or less risk tolerant than the logarithmic investor whose portfolio decisions are unaffected by the possibility of future learning. Numerical calculations show that uncertainty about the mean return on the market portfolio has a significant effect on the portfolio decision of an investor with a 20 year horizon if her assessment of the market risk premium is based solely on the Ibbotson and Sinquefield (1995) data.     

Audit Firm Portfolio Management Decisions

We examine client acceptance and client continuance decisions of a large audit firm to provide empirical evidence on the extent and nature of risk avoidance that the firm uses to purposefully manage its client portfolio. Our results support several key new inferences regarding audit firm portfolio management decisions. First, the results show that this firm is shedding the riskier clients in its portfolio, consistent with the risk avoidance theory of audit firm portfolio management. Second, the results show that the firm's newly accepted clients are less risky than its continuing clients. Although results of both the client continuance and client acceptance decisions imply a less risky portfolio emerging over time, there are greater differences in risk between continuing and discontinued clients than between continuing and newly accepted clients. Third, we find that audit risk factors are more important in audit firm portfolio management decisions than are financial risk factors. Finally, we find no evidence that audit pricing affects the client acceptance and continuance decisions of this firm, controlling for risk and other client characteristics.     

Investment Decisions Depend on Portfolio Disclosures

A weekly database of retail money fund portfolio statistics is uneconomical for retail investors to observe, so it allows direct comparison of disclosed and undisclosed portfolios. This makes possible a more direct and unambiguous test for "window dressing" than elsewhere in the literature. The analysis shows that funds allocating between government and private issues hold more in government issues around disclosures than at other times, consistent with the theory that intermediaries prefer to disclose safer portfolios. Cross-sectional comparisons locate the most intense rebalancing in the worst recent performers.     

Market Timing and Managerial Portfolio Decisions

This paper provides evidence that top managers have contrarian views on firm value. Managers' perceptions of fundamental value diverge systematically from market valuations, and perceived mispricing seems an important determinant of managers' decision making. Insider trading patterns shows that low valuation firms are regarded as undervalued by their own managers relative to high valuation firms. This finding is robust to controlling for noninformation motivated trading. Further evidence links managers' private portfolio decisions to changes in corporate capital structures, suggesting that managers try to actively time the market both in their private trades and in firm‐level decisions.     

Risks and Portfolio Decisions Involving Hedge Funds

This article characterizes the systematic risk exposures ofhedge funds using buy-and-hold and option-based strategies.Our results show that a large number of equity-oriented hedgefund strategies exhibit payoffs resembling a short positionin a put option on the market index and therefore bear significantleft-tail risk, risk that is ignored by the commonly used mean-varianceframework. Using a mean-conditional value-at-risk framework,we demonstrate the extent to which the mean-variance frameworkunderestimates the tail risk. Finally, working with the systematicrisk exposures of hedge funds, we show that their recent performanceappears significantly better than their long-run performance.     

Martingales and Portfolio Decisions: A User’s Guide

This article gives an overview and introduction to the Martingale approach to multi-period (dynamic) portfolio decisions. While Martingale pricing techniques have long been used with considerable success in the pricing of derivatives and financial assets in general, their potential to improve the practice of dynamic portfolio decisions is not sufficiently recognized yet. This article shows that the approach is, in principle, not difficult to implement for readers equipped with standard option replication techniques if markets are sufficiently “complete” in order to provide investors with the relevant information about the pricing of financial risks. The article provides a practical guide to implement the basic features of the approach in a binomial framework.     

控制权冲突、资本配置决策与投资组合选择

本文以长期股权投资和固定资产的投资组合选择为研究对象,从控制权私利的视角探讨了大股东自利性动机对资本配置决策的作用机理,并进行了相应的数值模拟。研究发现：（1）固定资产投资规模与长期股权投资高状态收益存在负相关关系,而长期股权投资规模则与其高状态收益概率正相关;（2）大股东自利性动机驱使下的资本配置决策偏离了分散持股时的资本配置水平,偏离程度会随着现金流权与控制权分离度的增加而展现出非线性变化态势。上述研究结论为当前有关加强上市公司大股东财务决策监管的政策导向提供了重要的经验启示。     

The Role of Real Estate in an Institutional Investor's Portfolio Revisited

Many papers have recently pointed out that institutional investors allocate only a very small fraction of their portfolio to real estate, much smaller than theory would dictate. This raises the question, are institutional investors underinvested in real estate equities? Or do we simply have the wrong priors? This paper is an attempt to provide some new insights into this asset allocation paradox. The key conclusions of the paper are several: First, unlike other assets, it would appear that real estate, and real estate diversification, pays off at the very time when the benefits are most needed, that is, when consumption growth opportunities are low. Second, real estate returns are predictable. In fact, the amount of predictability in real estate returns appears to be about the same as in stock returns. Third, real estate performs well in an asset-liability framework. Fourth, the chance of experiencing a large loss on real estate over a long horizon is quite small. We also report here that private sector commercial real estate investments represent between 6 and 12 percent of investable wealth in the United States. Thus, it follows (if one believes the capital asset pricing model) that if institutional investors were to invest more in real estate (up to 12 percent of their assets), they should be able to eliminate nonmarket or unique risk. All of this leaves us a bit dumbfounded as to why institutional investors hold only between 2 and 3 percent of their assets in real estate.     

A Simulation Approach to Dynamic Portfolio Choice with an Application to Learning About Return Predictability

We present a simulation-based method for solving discrete-timeportfolio choice problems involving non-standard preferences,a large number of assets with arbitrary return distribution,and, most importantly, a large number of state variables withpotentially path-dependent or non-stationary dynamics. The methodis flexible enough to accommodate intermediate consumption,portfolio constraints, parameter and model uncertainty, andlearning. We first establish the properties of the method forthe portfolio choice between a stock index and cash when thestock returns are either iid or predictable by the dividendyield. We then explore the problem of an investor who takesinto account the predictability of returns but is uncertainabout the parameters of the data generating process. The investorchooses the portfolio anticipating that future data realizationswill contain useful information to learn about the true parametervalues.     

The Role of Financial Appraisal in Decisions to Acquire Advanced Manufacturing Technology

There have been suggestions that the financial appraisal techniques which are commonly applied to capital expenditure proposals may be unsuitable for evaluating proposals concerned with the acquisition of advanced manufacturing technology. This paper reviews the arguments advanced to justify exempting such proposals from financial appraisal. It is argued that the case against financial appraisal is not substantiated. The difficulties cited by the critics of financial appraisal can be resolved by better management of the appraisal process.     

Introducing a Learning Portfolio in an Undergraduate Financial Accounting Course

This paper evaluates changes made to the internal assessment component of a third year financial accounting course at a university in New Zealand. A learning portfolio was designed to supplement existing coursework. The aim was to engender in students a deep rather than a surface approach to learning. As a record of the students' learning, the learning portfolio was an attempt to produce an innovative development in the assessment of what was a traditionally taught financial accounting course. Within their learning portfolios, students were required to complete a number of tasks, each aimed at improving critical thinking skills and creativity. Students were also required to maintain a personal or reflective section aimed at personalising and deepening the quality of their learning.     

Dynamic Portfolio Selection by Augmenting the Asset Space

We present a novel approach to dynamic portfolio selection that is as easy to implement as the static Markowitz paradigm. We expand the set of assets to include mechanically managed portfolios and optimize statically in this extended asset space. We consider “conditional” portfolios, which invest in each asset an amount proportional to conditioning variables, and “timing” portfolios, which invest in each asset for a single period and in the risk‐free asset for all other periods. The static choice of these managed portfolios represents a dynamic strategy that closely approximates the optimal dynamic strategy for horizons up to 5 years.     

The Role of Alternative Methodology on the Relation Between Portfolio Size and Diversification

An important concern in portfolio management is the number of securities needed to create a well-diversified portfolio. The number of securities that constitute a welldiversified portfolio, however, varies widely among studies. It is demonstrated that past conclusions are highly sensitive to the methodology used in quantifying diversification. This finding motivates the development of alternative methods that reduce the effect of repeated replications on test results. The first approach exploits the power curves of statistical tests, whereas the second approach suggests the use of more robust statistics. Both approaches provide researchers with guidance in the design of future diversification studies.     

From Stock Selection to Portfolio Alpha Generation: The Role of Fundamental Analysis

In this roundtable sponsored by Columbia Business School's Center for Excellence in Accounting Research and Security Analysis, a group of successful investors discuss their approaches and methods. A common saying among financial economists is that stock prices are set not by the average investor, but “at the margin” by the most sophisticated and influential investors. The intent of this roundtable is to furnish a portrait of such “marginal” investors, one that turns out to be quite different from the quarterly earnings‐driven, momentum traders often depicted by the media and deplored by corporate executives. In response to the common charge of short termism leveled by corporate managers, most of the investors at the table claimed to take large, multi‐year positions in companies they believed to be well‐managed, but temporarily undervalued. Instead of being attracted to earnings momentum, and rather than simply capitalizing current earnings at industry‐wide multiples to arrive at price targets, the analysis of these investors begins with a “deep dive” into a company's financials, which is often reinforced by primary research—visits with management, customers, suppliers. The aim of such research is to identify, well before the broad market does, companies that promise to earn consistently high and sustainable returns on invested capital.     

Principles of Financial Regulation: A Dynamic Portfolio Approach

Economists seeking explanations for the global financial crisisof 1997–99 are reaching consensus that a major factorwas weak financial institutions, which resulted in part frominadequate government regulations. At the same time many developingcountries are struggling with an overregulated financial system—onethat stifles innovation and the flow of credit to new entrepreneursand that can stunt the growth of well-established firms. Inparticular, too many countries are relying excessively on capitaladequacy standards, which are inefficient and sometimes counterproductive.The author argues that financial systems can be reformed successfullyusing a "dynamic portfolio approach" aimed at managing the incentivesand constraints that affect not only financial institutions'exposure to risk but also their ability to cope with it. Thearticle sets out general principles of financial regulationand shows how the dynamic portfolio approach can help countriesdeal with the special problems that arise during the transitionto a more liberalized economy as well as those that arise indealing with a financial crisis similar to the 1997 crisis inEast Asia.      

Sequential Learning,Predictability, and Optimal Portfolio Returns

This paper finds statistically and economically significant out‐of‐sample portfolio benefits for an investor who uses models of return predictability when forming optimal portfolios. Investors must account for estimation risk, and incorporate an ensemble of important features, including time‐varying volatility, and time‐varying expected returns driven by payout yield measures that include share repurchase and issuance. Prior research documents a lack of benefits to return predictability, and our results suggest that this is largely due to omitting time‐varying volatility and estimation risk. We also document the sequential process of investors learning about parameters, state variables, and models as new data arrive.     

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.     

Dynamic Consumption and Portfolio Choice with Stochastic Volatility in Incomplete Markets

This paper examines the optimal consumption and portfolio-choiceproblem of long-horizon investors who have access to a risklessasset with constant return and a risky asset ("stocks") withconstant expected return and time-varying precision—thereciprocal of volatility. Markets are incomplete, and investorshave recursive preferences defined over intermediate consumption.The paper obtains a solution to this problem which is exactfor investors with unit elasticity of intertemporal substitutionof consumption and approximate otherwise. The optimal portfoliodemand for stocks includes an intertemporal hedging componentthat is negative when investors have coefficients of relativerisk aversion larger than one, and the instantaneous correlationbetween volatility and stock returns is negative, as typicallyestimated from stock return data. Our estimates of the jointprocess for stock returns and precision (or volatility) usingU.S. data confirm this finding. But we also find that stockreturn volatility does not appear to be variable and persistentenough to generate large intertemporal hedging demands.     

Learning Portfolio Management by Experience: University Student Investment Funds

In this age of greater cooperation between academia and industry, it is surprising to find a general lack of awareness by both parties as to the progress being made to closely integrate financial theory with practice. This paper is intended to bring colleagues in universities and business up to date in an area where considerable success has been achieved, namely, investments and portfolio management. Through a survey of universities across the country, a comprehensive list of programs that allow students to manage portfolios of real dollars has been compiled. It is hoped that sharing the results of this survey will encourage further cooperation in establishing new innovative programs in all areas of business.