Look at the label on a jar of supermarket pasta sauce and try to trace how it reached you. The tomatoes may have been grown in one country, cooked down in a second, packed in glass made in a third and trucked across a fourth. A food system is the whole chain of farms, firms, workers, rules and habits that moves food from soil to plate and on to the trash. In rich countries, and increasingly in poor ones, that chain has grown long, efficient and hard to see.

Farm to fork

Farming is now a small part of the food economy. Most of the money spent on food pays for what happens after the farm gate: processing, packaging, transport, retail, restaurants, energy and marketing. In the United States, government estimates suggest that farmers receive only around fifteen cents of each food dollar, with the rest going to the businesses that turn crops into meals. This matters for debates about food prices. A spike in wheat prices barely moves the price of a loaf, because the wheat is a small part of what the shopper pays for.

At the same time, the world eats a narrow range of crops. Of the thousands of plant species humans have eaten, a handful dominate. Rice, wheat and maize supply roughly half of all the calories people eat. Soybeans, much of which become animal feed, and palm oil fill out the core of the global diet.

Concentration and trade

Many links in the chain are controlled by a few firms. Four trading companies, often called the ABCD group (ADM, Bunge, Cargill and Louis Dreyfus), handle a large share of the world's grain and oilseed trade. In the United States, four meatpacking companies process about 85 percent of the beef. A few firms dominate seeds, farm chemicals and supermarket retail in many countries. Defenders say that scale brings efficiency and cheap food. Critics answer that when a few buyers dominate, farmers have little bargaining power, and the system becomes fragile, since trouble at one plant or port spreads quickly.

Trade lets regions specialize, as the economics course explains, and lets a dry country import the water embodied in grain grown elsewhere. Egypt, for example, imports much of its wheat. But reliance on imports exposes buyers to shocks. In 2007 and 2008, high oil prices, poor harvests, demand for biofuels and export bans together drove grain prices sharply up, and food protests broke out in dozens of countries. When Russia invaded Ukraine in 2022, shipments from two of the world's largest grain exporters were thrown into doubt, and prices jumped again.

Lean and fragile

Modern supply chains are lean. Supermarkets keep small stocks and rely on frequent deliveries. That works well in normal times and poorly in a sudden shock. In 2020, early in the pandemic, farmers dumped milk and plowed under vegetables while some store shelves sat empty. The food existed, but it was packed for restaurants and schools that had closed, in bulk sizes that the retail chain could not easily handle. Switching packaging lines, labels and trucking routes took weeks.

Waste is another feature of the system. The UN Food and Agriculture Organization estimates that about 13 percent of food is lost between harvest and retail, and the UN Environment Programme estimates that close to another fifth is wasted in shops, restaurants and homes. In poorer countries more food is lost near the farm; in richer countries more is wasted near the plate, through spoilage without refrigeration on one side and overbuying and strict cosmetic standards on the other.

Safety and trust

A long chain also raises the question of trust. A person who buys meat from a neighbor can see the animal. A person who buys a shrink-wrapped package from a distant plant must rely on rules. In 1906 Upton Sinclair's novel The Jungle exposed filthy conditions in Chicago's meatpacking plants. Sinclair had meant to arouse sympathy for the immigrant workers, and he later wrote, "I aimed at the public's heart, and by accident I hit it in the stomach." Public outrage led that same year to the Pure Food and Drug Act and the Meat Inspection Act, early examples of government inspection standing in for personal knowledge of the seller. Food safety rules, labeling and inspection remain the scaffolding that lets strangers trust each other's food.

Worked example: a winter strawberry

Picture a box of strawberries on sale in a northern supermarket in February. They were probably grown in a warm, dry region in open fields or under plastic tunnels, picked by hand by seasonal workers, many of them migrants. They were chilled within hours, then trucked or flown to a distribution center and on to the store. Each step adds cost, and each also creates jobs.

The strawberry raises every theme of this level. The farmer gets a small slice of the price. A few large distributors and retailers set terms. The chain depends on fuel, refrigeration and a steady supply of workers whose wages and conditions shoppers never see. If a border closes or a heat wave strikes, the box may vanish from the shelf. And if the berries go soft before they sell, they may join the large share of food that is thrown away. None of this means the shopper should feel guilty. It means the price on the box is only part of the story.