Before the introduction of stock index futures, some institutions tend to gradually strengthen the selection of the underlying index constituent stocks, which will lead to some funds gradually focusing on the allocation of heavyweights. However, this transfer should be carried out when the weight and investment opportunities of non-weighted stocks are equal. Institutions will not buy weights for the sake of buying weights, but will only pay more attention to heavyweights under the same conditions. So this tendency should exist, but it is difficult to be significant. However, market sentiment will gradually strengthen this effect, and it is likely to strengthen the premium effect of heavyweights before the launch of this futures index under the irrational impetus of speculation.

Because the premium of heavyweights before the introduction of stock index futures contains too many emotional speculation factors, we expect that the heavyweights are likely to fall on the eve of the listing of stock index futures. The main motive force of cash-out of speculative funds will still be the self-realization of market awareness. Because in the limited and referable foreign historical cases, the probability of spot index falling after the introduction of futures index is too large, the conclusion drawn from this small sample case has been gradually recognized by investors in the marketing of most institutions.

The long-term trend of the underlying spot index is determined by the fundamentals of the underlying index and will not change because of the introduction of derivative products. Derivative products are just game tools based on spot products, and the decision order of the three must be "fundamentals-spot index-index derivative products". What's more, the number of constituent stocks in the Shanghai and Shenzhen 300 Index is only 300. Although constituent stocks significantly represent all A shares, they are only a part of the whole spot market.