On the estimation of the shape parameter of the gamma distribution in second-order asymptotics

In the two-parameter case with parameter orthogonality, we propose a method of constructing an estimator with second-order admissibility under any loss function with a given loss coefficient. Furthermore, we give a sufficient condition for any estimator to be second-order admissible or inadmissible. On the basis of these results, the problem of estimating the shape parameter of the gamma distribution is discussed at the level of second-order asymptotics.