Benchmark priors for Bayesian model averaging
Article Abstract:
In contrast to a posterior analysis given a particular sampling model, posterior model probabilities in the context of model uncertainty are typically rather sensitive to the specification of the prior. In particular, 'diffuse' priors on model-specific parameters can lead to quite unexpected consequences. Here we focus on the practically relevant situation where we need to entertain a (large) number of sampling models and we have (or wish to use) little or no subjective prior information. We aim at providing an `automatic' or `benchmark' prior structure that can be used in such cases. We focus on the normal linear regression model with uncertainty in the choice of regressors. We propose a partly non-informative prior structure related to a natural conjugate g-prior specification, where the amount of subjective information requested from the user is limited to the choice of a single scalar hyperparameter [g.sub.oj]. The consequences of different choices for [g.sub.oj] are examined. We investigate theoretical properties, such as consistency of the implied Bayesian procedure. Links with classical information criteria are provided. More importantly, we examine the finite sample implications of several choices of [g.sub.oj] in a simulation study. The use of the [MC.sup.3] algorithm of Madigan and York (Int. Stat. Rev. 63 (1995) 215), combined with efficient coding in Fortran, makes it feasible to conduct large simulations. In addition to posterior criteria, we shall also compare the predictive performance of different priors. A classic example concerning the economics of crime will also be provided and contrasted with results in the literature. The main findings of the
Publication Name: Journal of Econometrics
Subject: Economics
ISSN: 0304-4076
Year: 2001
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GENERALIZED AUTOREGRESSIVE CONDITIONAL HETEROSKEDASTICITY
Article Abstract:
A natural generalization of the ARCH (Autoregressive Conditional Heteroskedastic) process introduced in Engle (1982) to allow for past conditional variances in the current conditional variance equation is proposed. Stationarity conditions and autocorrelation structure for this new class of parametric models are derived. Maximum likelihood estimation and testing are also considered. Finally an empirical example relating to the uncertainty of the inflation rate is presented.
Publication Name: Journal of Econometrics
Subject: Economics
ISSN: 0304-4076
Year: 2001
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Notes on financial econometrics
Article Abstract:
The first part of the discussion reviews recent successes in modeling of discrete time financial data and argues that a direct approach is better suited than stochastic volatility. The second part reviews recent work on estimating continuous time models with emphasis on simulation-based techniques and joint estimation of the risk neutral and objective probability distributions. [C] 2001 Elsevier Science S.A. All rights reserved.
Publication Name: Journal of Econometrics
Subject: Economics
ISSN: 0304-4076
Year: 2001
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