diff --git a/doc/dynare.texi b/doc/dynare.texi index 731692d33..d48175b6f 100644 --- a/doc/dynare.texi +++ b/doc/dynare.texi @@ -4353,10 +4353,20 @@ Specifies a starting value for the posterior mode optimizer or the maximum likelihood estimation. If unset, defaults to the prior mean. @item @var{LOWER_BOUND} -Specifies a lower bound for the parameter value in maximum likelihood estimation +@anchor{lower_bound} Specifies a lower bound for the parameter value in maximum +likelihood estimation. In a Bayesian estimation context, sets a lower bound +only effective while maximizing the posterior kernel. This lower bound does not +modify the shape of the prior density, and is only aimed at helping the +optimizer in identifying the posterior mode (no consequences for the MCMC). For +some prior densities (namely inverse gamma, gamma, uniform or beta) it is +possible to shift the default lower bound (zero) on the left or the right using +@ref{prior_3rd_parameter}. In this case the prior density is effectively +modified (note that the truncated Gaussian density is not implemented in +Dynare). If unset, defaults to minus infinity (ML) or the natural lower bound +of the prior (Bayesian estimation). @item @var{UPPER_BOUND} -Specifies an upper bound for the parameter value in maximum likelihood estimation +Same as @ref{lower_bound}, but specifying an upper bound instead. @item @var{PRIOR_SHAPE} A keyword specifying the shape of the prior density. @@ -4368,16 +4378,18 @@ that @code{inv_gamma_pdf} is equivalent to @code{inv_gamma1_pdf} @item @var{PRIOR_MEAN} -The mean of the prior distribution +@anchor{prior_mean} The mean of the prior distribution @item @var{PRIOR_STANDARD_ERROR} -The standard error of the prior distribution +@anchor{prior_standard_error} The standard error of the prior distribution @item @var{PRIOR_3RD_PARAMETER} +@anchor{prior_3rd_parameter} A third parameter of the prior used for generalized beta distribution, generalized gamma and for the uniform distribution. Default: @code{0} @item @var{PRIOR_4TH_PARAMETER} +@anchor{prior_4th_parameter} A fourth parameter of the prior used for generalized beta distribution and for the uniform distribution. Default: @code{1} @@ -5731,16 +5743,29 @@ estimates using a higher tapering are usually more reliable. @deffn Command model_comparison @var{FILENAME}[(@var{DOUBLE})]@dots{}; @deffnx Command model_comparison (marginal_density = laplace | modifiedharmonicmean) @var{FILENAME}[(@var{DOUBLE})]@dots{}; - +@anchor{model_comparison} @descriptionhead -This command computes odds ratios and estimate a posterior density -over a collection of models -(see e.g. @cite{Koop (2003), Ch. 1}). The priors over models can be specified -as the @var{DOUBLE} values, otherwise a uniform prior over all models is assumed. -In contrast to frequentist econometrics, the models to be compared do not need to be nested. -However, as the computation of posterior odds ratios is a Bayesian technique, -the comparison of models estimated with maximum likelihood is not supported. +This command computes odds ratios and estimate a posterior density over a +collection of models (see e.g. @cite{Koop (2003), Ch. 1}). The priors over +models can be specified as the @var{DOUBLE} values, otherwise a uniform prior +over all models is assumed. In contrast to frequentist econometrics, the +models to be compared do not need to be nested. However, as the computation of +posterior odds ratios is a Bayesian technique, the comparison of models +estimated with maximum likelihood is not supported. + +It is important to keep in mind that model comparison of this type is only +valid with proper priors. If the prior does not integrate to one for all +compared models, the comparison is not valid. This may be the case if part of +the prior mass is implicitly truncated because Blanchard and Kahn conditions +(instability or indeterminacy of the model) are not fulfilled, or because for +some regions of the parameters space the deterministic steady state is +undefined (or Dynare is unable to find it). The compared marginal densities +should be renormalized by the effective prior mass, but this not done by +Dynare: it is the user's responsibility to make sure that model comparison is +based on proper priors. Note that, for obvious reasons, this is not an issue if +the compared marginal densities are based on Laplace approximations. + @examplehead