3,314 research outputs found

    Optimal diversification in the presence of parameter uncertainty for a risk averse investor

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    We consider an investor who faces parameter uncertainty in a continuoustime financial market. We model the investor's preference by a power utility function leading to constant relative risk aversion. We show that the loss in expected utility is large when using a simple plug-in strategy for unknown parameters. We also provide theoretical results that show the trade-off between holding a well-diversified portfolio and a portfolio that is robust against estimation errors. To reduce the effect of estimation, we constrain the weights of the risky assets with an L1-norm leading to a sparse portfolio. We provide analytical results that show how the sparsity of the constrained portfolio depends on the coefficient of relative risk aversion. Based on a simulation study, we demonstrate the existence and the uniqueness of an optimal bound on the L1-norm for each level of relative risk aversion

    Optimal diversification in the presence of parameter uncertainty for a risk averse investor

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    We consider an investor who faces parameter uncertainty in a continuoustime financial market. We model the investor's preference by a power utility function leading to constant relative risk aversion. We show that the loss in expected utility is large when using a simple plug-in strategy for unknown parameters. We also provide theoretical results that show the trade-off between holding a well-diversified portfolio and a portfolio that is robust against estimation errors. To reduce the effect of estimation, we constrain the weights of the risky assets with an L1-norm leading to a sparse portfolio. We provide analytical results that show how the sparsity of the constrained portfolio depends on the coefficient of relative risk aversion. Based on a simulation study, we demonstrate the existence and the uniqueness of an optimal bound on the L1-norm for each level of relative risk aversion

    Diversification Preferences in the Theory of Choice

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    Diversification represents the idea of choosing variety over uniformity. Within the theory of choice, desirability of diversification is axiomatized as preference for a convex combination of choices that are equivalently ranked. This corresponds to the notion of risk aversion when one assumes the von-Neumann-Morgenstern expected utility model, but the equivalence fails to hold in other models. This paper studies axiomatizations of the concept of diversification and their relationship to the related notions of risk aversion and convex preferences within different choice theoretic models. Implications of these notions on portfolio choice are discussed. We cover model-independent diversification preferences, preferences within models of choice under risk, including expected utility theory and the more general rank-dependent expected utility theory, as well as models of choice under uncertainty axiomatized via Choquet expected utility theory. Remarks on interpretations of diversification preferences within models of behavioral choice are given in the conclusion

    Portfolio Optimization and Ambiguity Aversion

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    This thesis analyses whether considering ambiguity aversion in portfolio optimization improves the out-of-sample performance of portfolio optimization approaches. Furthermore, it is assessed which role ambiguity aversion plays in improving the portfolio performance, especially compared with the role of estimation errors. This is done by evaluating the out-of-sample performance of the approach of Garlappi, Uppal and Wang for an investor with multiples priors and aversion to ambiguity compared to other portfolio optimization strategies from the literature not taking ambiguity aversion into account. It is shown that considering ambiguity aversion in portfolio optimization can improve the out-of-sample performance compared to the sample based mean-variance model and the Bayes-Stein model. However, the minimum-variance model and the model of naĂŻve diversification, which are both independent of expected returns, outperform the approach considering ambiguity aversion for most of the empirical applications shown in this thesis. These results indicate that ambiguity aversion does play a role in portfolio optimization, however, estimation errors regarding expected returns overshadow the benefits of optimal asset allocation. Keywords: portfolio choice; asset allocation; estimation error; ambiguity; uncertainty

    How many stocks make a diversified portfolio in a continuous-time world?

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    Abstract. This thesis aims to answer how many stocks make a diversified portfolio in a continuous-time world. The study investigates what are the factors determining diversification effects in a real, continuous-time, world as opposed to thoroughly studied theoretical single period world. Continuous-time world investors care about geometric, instead of arithmetic, rate of return. We show how methodology based on information theory can be utilized in investing context. Geometric risk premium is explained by the Shannon limit and its derivative, fractional Kelly criterion. Investing world counterpart for the Shannon limit, compounding process capacity, is derived. Geometric risk premium is decomposed to single stock risk premium and diversification premium. Method for estimating diversification premium is provided. Concept of realizable risk premium is derived and used in risk averse investor diversification metrics. Diversification effect is measured as a (realizable) risk premium ratio and as a (realizable) gross compound excess wealth ratio. Both ratios are between a randomly selected portfolio of selected size and fully diversified benchmark. We show, both analytically and empirically, that diversification in a continuous-time world is a negative price lunch as opposed to free lunch in a single period world. Investor is paid a diversification premium, implying higher geometric risk premium, for consuming a lunch. The magnitude of diversification premium difference to benchmark, the opportunity cost of foregone diversification, is shown to be equal to one half of portfolio’s idiosyncratic variance scaled by squared investment fraction. To maintain a constant wealth ratio, required level of diversification for a long-term risk neutral investor is approximately directly proportional to investment time horizon length. The factors determining required level of diversification in a continuous-time world are number of stocks in the benchmark, Sharpe ratio and variance of the benchmark, idiosyncratic variance of an average stock, investment fraction and time. At investment fraction 1.0, risk averse investor requires more than 100, 200 or 1000 stocks to achieve 90%, 95% or 99% of the maximum diversification benefit, respectively. For short-term risk neutral investor, the corresponding numbers are about 20, 40 or 200 stocks and yet significantly more for long-term risk neutral investor. The numbers increase and decrease as investment fraction increase and decrease, respectively. We find that small firms require substantially more diversification compared to large firms and that there are substantial and consistent differences in diversification premiums between investing styles

    A Behavioural Approach To Financial Puzzles

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    Many financial puzzles have been solved, at least partially, by the introduction of alternative assumptions on the behaviour of investors. Cumulative prospect theory and mental accounting are two such approaches which are used in this paper to analyze some of the most important financial puzzles. We first focus our attention on anomalies (or considered as such in the standard expected utility model) at the individual level, for example the disposition effect or the low diversification puzzle. We then address two aggregate puzzles, namely the equity premium puzzle and the return predictability puzzle. We show how recent behavioral models allow to explain these anomalies in a very natural way.

    Optimal Timing in Trading Japanese Equity Mutual Funds: Theory and Evidence

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    This paper provides both theoretical and empirical analyses of market participants' optimal decision-making in trading Japanese equity mutual funds. First, we build an intertemporal decision-making model under uncertainty in the presence of transaction costs. This setting enables us to shed light on the investors' option to delay investment. A comparative analysis shows that an increase in uncertainty over the expected rate of return on mutual funds has a negative impact not only on market participants' buying behavior but also on their selling behavior. In addition, a several percent increase in front-end loads and redemption fees is likely to change the optimal holding ratio of mutual funds in investors' portfolios, by up to 10 percent. Second, we empirically examine the theoretical implications using daily transaction data of selected equity mutual funds in Japan. By estimating a panel data model, we conclude that for the sample period, from August 2000 to July 2001, investment behavior has been rational in light of our theoretical model. Our results suggest that investors are likely to rationally postpone their purchases of equity mutual funds under the present circumstances of low expected returns, high degree of uncertainty, and high trading costs.

    Which heuristics can aid financial-decision-making?

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    © 2015 Elsevier Inc. We evaluate the contribution of Nobel Prize-winner Daniel Kahneman, often in association with his late co-author Amos Tversky, to the development of our understanding of financial decision-making and the evolution of behavioural finance as a school of thought within Finance. Whilst a general evaluation of the work of Kahneman would be a massive task, we constrain ourselves to a more narrow discussion of his vision of financial-decision making compared to a possible alternative advanced by Gerd Gigerenzer along with numerous co-authors. Both Kahneman and Gigerenzer agree on the centrality of heuristics in decision making. However, for Kahneman heuristics often appear as a fall back when the standard von-Neumann-Morgenstern axioms of rational decision-making do not describe investors' choices. In contrast, for Gigerenzer heuristics are simply a more effective way of evaluating choices in the rich and changing decision making environment investors must face. Gigerenzer challenges Kahneman to move beyond substantiating the presence of heuristics towards a more tangible, testable, description of their use and disposal within the ever changing decision-making environment financial agents inhabit. Here we see the emphasis placed by Gigerenzer on how context and cognition interact to form new schemata for fast and frugal reasoning as offering a productive vein of new research. We illustrate how the interaction between cognition and context already characterises much empirical research and it appears the fast and frugal reasoning perspective of Gigerenzer can provide a framework to enhance our understanding of how financial decisions are made

    Cross-border Risk Transmission by a Multinational Bank

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    A model of international banking, with the stress on the specific management human capital (borrower monitoring) and the majority shareholder human capital (manager auditing) is used to study the effects of exogenous shocks in one country on credit creation in the other. I show that the presence of the two named categories of non-transferable skills in the banking technology reduces the role of the standard portfolio diversification motive for cross-border transmission of disturbances. At the same time, this bank-specific market friction creates a separate channel of shock propagation, a function of the bank shareholder and manager incentives. It can even happen that the exogenous shock impact on credit has a different sign in the “relationship“ as opposed to “arm’s length“ banking environment. This phenomenon, caused by the marginal effect of the manager human capital involvement in the bank operation, is present in the bank branches with relatively small loan volumes. When the loan volume is large, the direction of the manager-auditing bank reaction to shocks abroad is the same as that of an arm’s length lender.multinational bank; managerial effort; audit; credit; foreign shock

    The optimal currency composition of external debt

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    The increased volatility of exchange rates, interest rates and goods prices has focused fresh attention on the importance for developing countries of reducing their risks in these markets. Although, these countries generally cannotuse such conventional hedging instruments as currency and commodity futures, they can use the currency composition of their external debt to hedge against exchange rates and commodity prices. In this line, this paper uses findings from the literature on optimal portfolio theory to discuss the optimal currency composition of external debt. The analysis considers a small open economy facing a perfect world capital market and a large number of perfect commodity markets. The paper derives the optimal currency composition of the country's aggregate assets and external liabilities and describes the necessary estimations and computations, including how to take into account the currency composition of existing external liabilities.Economic Theory&Research,Environmental Economics&Policies,Fiscal&Monetary Policy,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Financial Intermediation
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