Unstable Weights in the Combination of Forecasts
研究发现预测组合中的权重非常不稳定，导致组合预测效果常不如单个预测或简单平均。通过蒙特卡洛实验和实际GNP预测数据验证，建议实践中使用简单平均。
The weights used in the combination of forecasts are shown to be very unstable. They are generally so unstable that the combined forecasts often do not perform better than some of the individual forecasts or a simple average of the forecasts in practice. The instability is found from a series of Monte Carlo experiments as well as from the nominal GNP forecasts from four well-known macro forecasters. The Monte Carlo experiments also show that when the underlying models are known, a composite forecast from a composite model is generally more accurate than the combination of the individual forecasts. A simple average is shown to be the best technique to use in practice, because the weights in the combination are so unstable.