The reduced rank regression model arises repeatedly in theoretical and
applied econometrics. To date the only general treatments of this mod
el have been frequentist. This paper develops general methods for Baye
sian inference with noninformative reference priors in this model, bas
ed on a Markov chain sampling algorithm, and procedures for obtaining
predictive odds ratios for regression models with different ranks. The
se methods are used to obtain evidence on the number of factors in a c
apital asset pricing model.