Table 5. Contrastive experiments.

Model	Stock market index	Decomposition method	Denoising method	Forecasting model
CEEMD-CNN-LSTM (Rezaei, Faaljou & Mansourfar, 2021)	S&P500, DJI, DAX, Nikkei225	Single level CEEMD	–	CNN-LSTM
CEEMDAN-LSTM (Cao, Li & Li, 2019)	S&P500, DAX, HSI, SSE	Single level CEEMDAN	–	LSTM
CAL (Lv et al., 2022)	S&P500, DAX, HSI, SSE	Single level CEEMDAN	Augmented Dickey Fuller Test	ARMA-LSTM
GRU based on CEEMDAN-Wavelet (Qi, Ren & Su, 2023)	S&P500, CSI300	Single level CEEMDAN	Wavelet transform	GRU
2LE-CEEMDAN-LSTM-SVR	S&P500, DAX, DJI, SSE	Two level CEEMDAN	Entropy ratio-based	LSTM-SVR