The next time you're at a grocery store, let the cashier ring up the sale. Then try to bargain for a better deal. Sounds ridiculous, doesn't it? After all, just a handful of retailers sell more than half of all the groceries in the United States, and an individual shopper has very little power to negotiate. That same imbalance of power is a real problem for farmers and ranchers in the United States. Farmers are proud of their independence, but having millions of growers bartering separately puts them at a real disadvantage in the marketplace. That is why they banded...