Smooth coefficient estimation of a seemingly unrelated regression

This paper proposes estimation and inference for the semiparametric smooth coefficient seemingly unrelated regression model. We discuss the imposition of cross-equation restrictions which are required by economic theory as well as methods for data driven bandwidth selection. A test of correct functional form for the entire system of equations is also constructed. Asymptotic and finite sample results are given. We illustrate our estimator by applying it to a cost system for US commercial banks. Our results show that most of the banks are operating under increasing returns to scale, but that returns to scale decrease with bank size.