The value of stock index futures varies in direct proportion to changes in these indexes. (marketfinancenews.com)
After all, a trend - following portfolio will probably have a significant fraction of their risk allocated to strategies on stock index futures. (winton.com)
This is typical for stock index futures, treasury bond futures, and futures on physical commodities when they are in supply (e.g. agricultural crops after the harvest). (en.wikipedia.org)