A common procedure when combining two multivariate unbiased estimates (or forecasts) is the covariance adjustment technique (CAT). Here the optimal combination weights depend on the covariance structure of the estimators. In practical applications, however, this covariance structure is hardly...

When a forecaster predicts the future value of a certain random variable it is very likely that he will not only forecast that certain variable but he will also forecast other variables from the same field. In the literature on the combination of several individual forecasts univariate...