An invariance property of Farebrother's procedure for estimation with aggregated data

A procedure proposed by Farebrother (1979) for estimating the parameters of a standard Gauss-Markov model from aggregated data is shown to be invariant with respect to the choice of a generalized inverse of the matrix designated to approximate the unknown dispersion matrix of a transformed model, thus correcting Farebrother's statement that this desirable property cannot be attributed to his procedure.