At the grocery store, processed foods like cereal, crackers and candy usually maintain the same price for a long time, and inch up only gradually. Economists call these prices "sticky" because they don't move much even as some of the commodities that go into them do.
Take corn, for example, which can be a major food player as a grain, a starch or a sweetener.
Corn prices can fluctuate widely, so why don't products containing corn also see price changes? Why does your cereal pretty much cost $3 per box every week?
It's partly thanks to the futures market.