A Novel Shrinkage Estimator of the Covariance Matrix for Hierarchical Time Series
摘要
Reconciling hierarchical forecasts requires estimating the covariance matrix of the residuals, usually done by shrinking the off-diagonal elements of the sample covariance matrix. We propose a novel Double Shrinkage estimator (DS), which incorporates conditional dependence information suggested by the hierarchical structure. To validate these dependency assumptions, we analyze real datasets. Additionally, we evaluate the effectiveness of DS both in covariance matrix estimation and in forecast reconciliation.