This question is an exact duplicate of:
What is the relationship between E-mini SPX futures and the SPX index. Besides the obvious, one is cash the other is a futures product. How does buying/selling in one product influence the other. If someone sells 1000 contracts of E-mini futures how does that affect the S&P500 Index?? The trade he made should only affect the futures market. The seller isn’t technically selling shares in each individual stock within the SP500, so how does the cash market adjust to the sell order within the futures market??