What does a producer group actually do to the supply curve?

Most of this course treats supply as a physical constraint. In some markets it is partly a policy variable — a group of producers agreeing to hold output below what they could physically produce. The oil market is the clearest example, and it is worth describing accurately rather than dramatically.

The mechanics, stated factually

OPEC (the Organization of the Petroleum Exporting Countries) was founded in 1960 and today comprises a dozen or so member states, which together produce roughly a quarter to a third of the world's crude oil. Since late 2016 it has coordinated with a wider group of non-member producers, notably Russia, under the label OPEC+, which together accounts for something on the order of 40% or more of global supply.

What the group does mechanically is simple: members agree production targets, and members hold output at or near those targets. Two consequences follow.

• Part of world supply stops behaving like a price-taker. In a textbook market, every producer maximises output at any price above its cost. Under a quota, some supply is withheld deliberately — so the supply curve has a policy-shaped kink in it.
• Spare capacity becomes the market's shock absorber. Withheld production is capacity that can be restored quickly. It is concentrated in a small number of members, and it is the single most-watched number in the oil market, because it determines how much of a disruption the world can physically replace. Thin spare capacity turns an ordinary outage into a price event; ample spare capacity absorbs it.

The cohesion problem

Producer groups are structurally unstable, for a reason worth understanding rather than memorising: restraint is a public good. If members cut output, the price rises for everyone — including non-members and including any member who quietly produces above quota. So each individual member's best move is to let the others cut. Layer on genuine differences of interest — reserve life, fiscal breakeven, population, spare capacity, sanctions — and unanimity is difficult by construction.

This shows up in the record in both directions:

• 1985-86: the largest producer abandoned the role of absorbing everyone else's output. Restraint collapsed and prices fell by roughly two-thirds within months.
• March 2020: talks between OPEC and its partners broke down as pandemic demand collapsed; output rose into a vanishing market. The following month, the group agreed the largest coordinated cut in its history.

There is also a slower feedback: sustained restraint holds prices above the cost of non-member supply, which finances competitors. US shale grew substantially through the 2010s in exactly that environment. A producer group that defends a price also subsidises its rivals.

Concentration is not unique to oil

A handful of countries dominate seaborne iron ore, cobalt, lithium refining, platinum-group metals and several agricultural exports, and governments periodically restrict exports of food or critical minerals. The specific institution differs; the analytical question is identical: how much of this market's supply is set by decision rather than by cost?

Try it now

1. A year of crude, as daily candles, is below. Producer-group meetings are scheduled and public, so the announcements land on known dates. Find the tallest few bars in the window and ask, for each one, whether that day looks like the market learning something or the market finishing a move it had already started.

2. Drop a Level at the price on the day before one of those bars, and another at the price a month later. Which is bigger — the reaction to the meeting, or the drift that followed it? Compliance, not communiqués, is usually the larger number.
3. For one non-energy commodity you follow, write down which two or three countries dominate supply. Concentration is a fact you can look up; its consequences are the mechanism you just learned.