There are many reasons for this, and it cannot be said that the decline of the index is due to the delivery of stock index futures. There is a saying in the market that the delivery date effect of stock index futures refers to that when the delivery date of a stock index futures contract approaches, both long and short parties involved in futures trading use various means to exert influence on futures and even spot prices in order to win favorable contract delivery date prices. In particular, because the stock index futures contract is based on the stock spot index and settled in cash according to the regulations, the spot index will almost play a decisive role in the stock index futures at the final delivery, so a large amount of funds will enter the spot market, which will lead to a sharp fluctuation of the stock index, thus forming the "delivery day effect".