Key categoriesWhy wheat, beef, milk and salmon behave so differently

Grains are the foundation of the system. They are eaten directly as bread, noodles and rice, and they are fed to animals, which turns them into meat, milk and eggs.

Wheat is the most internationally traded of the three. Around 25% of the world's wheat supply was traded internationally in 2018–2020, compared with 16% for corn ⁵. The big exporters include Russia, the European Union, Canada, Australia, the United States, Argentina and Ukraine. The big importers include Egypt, other North African and Middle Eastern countries, Indonesia and China.

Corn (maize) is mostly an animal feed, and in some countries, especially the United States, a large share goes into ethanol for fuel. That link to energy markets matters. When oil prices rise, ethanol becomes more valuable, and so does the corn used to make it.

Rice is different. It is the staple food for billions of people, but very little of it is traded. Only 9.2% of the world's rice supply was traded internationally in 2018–2020 ⁵.

That makes the world rice market thin. Global rice production for 2025/26 was projected at a record 538.7 million tonnes, while world trade for calendar 2026 was projected at 61.3 million tonnes ⁶.

Trade is also concentrated. India was projected to account for about 40% of world rice trade in 2026 ⁶.

When a thin market depends heavily on one exporter, that exporter's policy decisions carry a lot of weight. India restricted rice exports in 2023, and its exports fell as a result ⁷. For importing countries that rely on the world market for rice, a decision in New Delhi can matter more than the weather in their own fields.

Meat turns feed into protein, and each species does it on a different timescale.

The cycle matters most. A broiler chicken reaches slaughter weight in weeks. A pig takes around six months. Beef takes years, because a heifer must be raised and bred before her calf can be raised in turn. This is why beef markets move in long cycles. When producers rebuild herds, they hold back female cattle, which reduces supply further in the short term and pushes prices up before they fall.

Market access is granted plant by plant. Many importing countries approve individual processing plants rather than whole countries. A meat plant may need to be registered with the importer's authorities before it can ship there. Gaining, losing or suspending those registrations is one of the most common trade signals in meat.

Disease drives trade. Outbreaks of African swine fever, foot-and-mouth disease or avian influenza can close export markets overnight, and can cut an importing country's own production sharply, forcing it to buy more abroad. Biosecurity signals move meat markets more than almost any other category.

Different markets value different parts. Exporters aim to sell every part of an animal to the market that pays most for it. Prime cuts may go to high-income markets, while offal, feet and other parts go to markets in Asia where they are valued more highly. Losing access to one market can change the economics of a whole carcass.

Seafood is really many markets: salmon, shrimp, tuna, whitefish, squid and hundreds of other species, each with its own supply chain.

Farmed now leads wild. In 2022, aquaculture overtook capture fisheries as the main source of aquatic animal production for the first time ². Wild catches have been broadly stable for decades. Growth now comes from fish farming, mostly in Asia.

Heavily traded. Exports of aquatic animal products reached a record USD 192 billion in 2022 ².

Seafood often crosses borders more than once. Fish may be caught or farmed in one country, processed in another, and eaten in a third. This makes seafood unusually sensitive to rules of origin, tariffs and traceability requirements, and to trade disputes between the countries along the way.

Fruit and vegetables make up a huge part of what people eat, but behave the least like commodities.

Seasons drive trade. Much international trade in fresh produce fills gaps in the calendar. When it is winter in Europe and North America, grapes, apples, citrus and avocados arrive from South America, South Africa, Australia and New Zealand. This counter-seasonal trade is one of the main reasons fresh produce crosses the equator.

Rules matter enormously. Because fresh produce can carry pests and diseases, importing countries set strict plant health rules. Some require specific treatments or inspections, and some ban products from particular regions entirely. Residue limits on pesticides are another major barrier. Gaining or losing market access for a single fruit can take years of negotiation.

Retailers set the standards. Large supermarket groups often decide what varieties, sizes, packaging and certifications they will accept. For many exporters, retailer requirements matter as much as government rules.