In this paper we provide evidence on the presence of seasonal unit roots in aggregate U.S. data. The analysis is conducted using the approach developed by Hyllebcrg, Engle, Granger and Yoo (1990). We first derive the mechanics and asyrnptotics of the HEGY procedure for monthly data and use Monte...

This paper provides asymptotic confidence intervals for the largest autoregressive root of a time series when this root is close to one. The intervals are readily constructed either graphically or using tables in the Appendix. When applied to the Nelson-Plosser (1982) data set, the main...

The purpose of this paper is to apply the theory of Lie transformation groups as developed by the first author, and derive a testable model of production and technical change. The econometric model is then applied to data derived by F. Gollop and D. Jorgenson for U.S. manufacturing industries...