Estimation and Inference for Set-identi…ed Parameters Using Posterior Lower Probability Toru Kitagawa CeMMAP and Department of Economics, UCL First Draft: September 2010 This Draft: March, 2012 Abstract In inference about set-identi…ed parameters, it is known that the Bayesian probability state- ments about the unknown parameters do not coincide, even asymptotically, with the frequen- tist’scon…dence statements. This paper aims to smooth out this disagreement from a multiple prior robust Bayes perspective. We show that there exist a class of prior distributions (am- biguous belief), with which the posterior probability statements drawn via the lower envelope (lower probability) of the posterior class asymptotically agree with the frequentist con…dence statements for the identi…ed set. With such class of priors, we analyze statistical decision problems including point estimation of the set-identi…ed parameter by applying the gamma- minimax criterion. From a subjective robust Bayes point of view, the class of priors can serve as benchmark ambiguous belief, by introspectively assessing which one can judge whether the frequentist inferential output for the set-identi…ed model is an appealing approximation of his posterior ambiguous belief. Keywords: Partial Identi…cation, Bayesian Robustness, Belief Function, Imprecise Probability, Gamma-minimax, Random Set. JEL Classi…cation: C12, C15, C21. Email:
[email protected]. I thank Andrew Chesher, Siddhartha Chib, Jean-Pierre Florens, Charles Manski, Ulrich Müller, Andriy Norets, Adam Rosen, Kevin Song, and Elie Tamer for valuable discussions and comments. I also thank the seminar participants at Academia Sinica Taiwan, Cowles Summer Conference 2011, EC2 Conference 2010, MEG 2010, RES Annual Conference 2011, Simon Fraser University, and the University of British Columbia for helpful comments.