3,464 research outputs found

    Time--consistent investment under model uncertainty: the robust forward criteria

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    We combine forward investment performance processes and ambiguity averse portfolio selection. We introduce the notion of robust forward criteria which addresses the issues of ambiguity in model specification and in preferences and investment horizon specification. It describes the evolution of time-consistent ambiguity averse preferences. We first focus on establishing dual characterizations of the robust forward criteria. This offers various advantages as the dual problem amounts to a search for an infimum whereas the primal problem features a saddle-point. Our approach is based on ideas developed in Schied (2007) and Zitkovic (2009). We then study in detail non-volatile criteria. In particular, we solve explicitly the example of an investor who starts with a logarithmic utility and applies a quadratic penalty function. The investor builds a dynamical estimate of the market price of risk λ^\hat \lambda and updates her stochastic utility in accordance with the so-perceived elapsed market opportunities. We show that this leads to a time-consistent optimal investment policy given by a fractional Kelly strategy associated with λ^\hat \lambda. The leverage is proportional to the investor's confidence in her estimate λ^\hat \lambda

    DSGE Models and Central Banks

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    A novel risk assessment and optimisation model for a multi-objective network security countermeasure selection problem

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    Budget cuts and the high demand in strengthening the security of computer systems and services constitute a challenge. Poor system knowledge and inappropriate selection of security measures may lead to unexpected financial and data losses. This paper proposes a novel Risk Assessment and Optimisation Model (RAOM) to solve a security countermeasure selection problem, where variables such as financial cost and risk may affect a final decision. A Multi-Objective Tabu Search (MOTS) algorithm has been developed to construct an efficient frontier of non-dominated solutions, which can satisfy organisational security needs in a cost-effective manner

    Spanning tests in return and stochastic discount factor mean-variance frontiers: A unifying approach

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    We propose new spanning tests that assess if the initial and additional assets share the economically meaningful cost and mean representing portfolios. We prove their asymptotic equivalence to existing tests under local alternatives. We also show that unlike two-step or iterated procedures, single-step methods such as continuously updated GMM yield numerically identical overidentifyng restrictions tests, so there is arguably a single spanning test. To prove these results, we extend optimal GMM inference to deal with singularities in the long run second moment matrix of the influence functions. Finally, we test for spanning using size and book-to-market sorted US stock portfolios.Asset Pricing, Continuously Updated GMM, Generalised Empirical Likelihood, Generalised Inverse, Representing Portfolios, Singular Covariance Matrix

    Essays on risk and uncertainty in financial decision making: Bayesian inference of multi-factor affine term structure models and dynamic optimal portfolio choices for robust preferences

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    Thesis (Ph.D.)--Boston UniversityThis thesis studies model inference about risk and decision making under model uncertainty in two specific settings. The first part of the thesis develops a Bayesian Markov Chain Monte Carlo (MCMC) estimation method for multi-factor affine term structure models. Affine term structure models are popular because they provide closed-form solutions for the valuation of fixed income securities. Efficient estimation methods for parameters of these models, however, are not readily available. The MCMC algorithms developed provide more accurate estimates, compared with alternative estimation methods. The superior performance of the MCMC algorithms is first documented in a simulation study. Convergence of the algorithm used to sample posterior distributions is documented in numerical experiments. The Bayesian MCMC methodology is then applied to yield data. The in-sample pricing errors obtained are significantly smaller than those of alternative methods. A Bayesian forecast analysis documents the significant superior predictive power of the MCMC approach. Finally, Bayesian model selection criteria are discussed. Incorporating aspects of model uncertainty for the optimal allocation of risk has become an important topic in finance. The second part of the thesis considers an optimal dynamic portfolio choice problem for an ambiguity-averse investor. It introduces new preferences that allow the separation of risk and ambiguity aversion. The novel representation is based on generalized divergence measures that capture richer forms of model uncertainty than traditional relative entropy measures. The novel preferences are shown to have a homothetic stochastic differential utility representation. Based on this representation, optimal portfolio policies are derived using numerical schemes for forward-backward stochastic differential equations. The optimal portfolio policy is shown to contain new hedging motives induced by the investor's attitude toward model uncertainty. Ambiguity concerns introduce additional horizon effects, boost effective risk aversion, and overall reduce optimal investment in risky assets. These findings have important implications for the design of optimal portfolios in the presence of model uncertainty

    De Finetti and Markowitz mean variance approach to reinsurance and portfolio selection problems: a comparison

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    Based on a critical analysis of de Finetti's paper, where the mean variance approach in finance was early introduced to deal with a reinsurance problem, we offer an alternative interpretative key of such an approach to the standard portfolio selection one. We discuss analogies and differences between de Finetti's and Markowitz's geometrical approaches
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