It can only be said that in most cases, the index will fall on the delivery date, but not all of them will rise.

In general, the futures price is higher than the spot price, that is, the premium. On the delivery day, both sides will try their best to level their positions. The futures price is close to the spot price. The higher the premium, the higher the desire of bulls to close positions, and the easier the price to fall, while the futures market will affect the spot and drive the spot market to fall.