Many regression models have two dimensions, say time (<italic>t</italic> = 1,…,<italic>T</italic>) and households (<italic>i</italic> = 1,…,<italic>N</italic>), as in panel data, error components, or spatial econometrics. In estimating such models we need to specify the structure of the error variance matrix <italic>Ω</italic>, which is of dimension <italic>T N</italic> × <italic>T N</italic>. If <italic>T N</italic> is...

The exact finite sample behavior is investigated on the bias of multiperiod leastsquares forecasts in the normal autoregressive model <italic>y</italic><italic>null</italic> = α + β<italic>y</italic>_null + <italic>u</italic><italic>null</italic>. Necessary and sufficient conditions are given for the existence of the bias and an expression is presented which we use to obtain...

We consider the Breitung (2002, <italic>Journal of Econometrics</italic> 108, 343–363) statistic ξ_null, which provides a nonparametric test of the I(1) hypothesis. If ξ denotes the limit in distribution of ξ_null as <italic>n</italic> → ∞, we prove (Theorem 1) that 0 ≤ ξ ≤ 1/π², a result that holds under any...

In this article we aim to establish intuitively appealing and verifiable conditions for the first-order efficiency and asymptotic normality of ML estimators in a multi-parameter framework, assuming joint normality but neither the independence nor the identical distribution of the observations....