When I teach why futures markets are so neat–they help people hedge against risk–I lay out numerical examples with oil or corn. Some of the students always wonder a little about how the actual transactions are made and I tell them. But I’d never found a clear piece laying out the mechanics that I could refer them to.

Until now. In today’s Wall Street Journal, there’s a front-page article on why people in Nebraska are worried about the financial bill’s new regulation of futures markets. In it, the author, Michael M. Phillips, has a nice few paragraphs laying out the mechanics. Here are three key ones:

Here’s how Mr. Kreutz does it: Say in early summer he sees that the price for a Chicago Board of Trade futures contract on corn for delivery later in the year is $3.56 a bushel. If he likes the price, and wants to lock it in, he calls AgWest and sells a futures contract for 5,000 bushels. The futures contract is a derivative in which the price for corn is set now for exchange in the future, though no kernels will change hands. Instead, when the contract nears expiration, Mr. Kreutz and the buyer of his contract will settle–in effect–by check.
By fall, when Mr. Kreutz is ready to deliver his crop to the local co-op, the market price might have fallen by 50 cents. He’ll sell his actual corn for that lower amount. But he’ll make up the difference through his financial hedge. (Mr. Kreutz buys a new futures contract at the lower price to make good on his earlier promise, making up the 50 cents.) In all, he’ll have hit the price target he locked in earlier in the year, minus brokerage fees.
If the price rises during the summer, as it did during the food crisis two years ago, Mr. Kreutz has to pony up extra cash for his broker–a margin call–to maintain his positions. He recoups that by selling his actual corn at a higher price, but has to take a loss to meet the futures contract he signed earlier in the year, missing out on a windfall but ultimately meeting his target price.