Magnus, Jan R.; Muris, Chris - In: Econometric Theory 26 (2010) 01, pp. 301-310
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...