“…Several methods of finding the (optimal) combination forecast have been proposed in a large body of literature: for example, a weighted average of forecasts, with the weights adding up to unity (Granger & Ramanathan, 1984); trimming (Granger & Jeon, 2004); rankbased approaches (Aiolfi & Timmermann, 2006); a least-squares forecast averaging (Hansen, 2008b); a complete subset regression (Elliott et al, 2013); iterated (Lin et al, 2018) or depthweighted combinations (Lee & Sul, 2021). Recently, ML techniques have been proposed to select and weight appropriate individual forecasts using, for example, Lasso-based procedures (Diebold & Shin, 2019;Mascio et al, 2020;Freyberger et al, 2020); a combining method for sophisticated models with the historical average serving as shrinkage target (Zhang et al, 2020); or the Combination Elastic Net (Rapach & Zhou, 2020). However, in many practical applications, the simple average of candidate forecasts is more robust than more sophisticated combination approaches (Qian et al, 2019), a phenomenon known as the forecast combination puzzle.…”