Can a Government Hold a Price Steady? Buy the Surplus and Sell the Shortage

Commodity prices swing far more than most prices, because supply responds slowly to price and demand responds hardly at all, so a poor harvest or a new mine produces an enormous move. That hurts producers in a glut and consumers in a shortage and makes planning impossible for both. The scheme addresses it by holding a physical store, buying when the price falls below a floor and selling when it rises above a ceiling, which in principle keeps the price within a band while the store absorbs the variation. Nothing about the idea requires the price to be wrong, only that it moves too much.

The conditions are demanding and rarely all present:

• •A commodity that stores without spoiling or costing much to keep
• •Enough capital to buy heavily through a long period of surplus
• •A price band set close to the genuine long-run average
• •Agreement among producers, or the ability to act without it
• •Willingness to sell the store when the price rises, which is politically hard
• •No large producer outside the scheme undercutting it

Setting the price band is the decision that destroys most schemes, because it is made politically and producers dominate the politics. A band set above the market's long-run average means the scheme buys continuously and sells almost never, so the store grows without limit and the money runs out, which is the failure mode of nearly every historical case. Setting it correctly requires predicting a long-run average that nobody knows, and adjusting it downward later means telling producers their income will fall, which is exactly what a producer-run scheme will not do. Getting the band wrong upward converts a stabilisation scheme into a price support scheme that eventually collapses.

Abandoning physical stores has not removed the underlying problem, and the instruments that replaced them address it differently. Financial hedging lets an individual producer or buyer fix a price for future delivery without anybody holding anything, which transfers risk rather than suppressing the price movement, and is what most large commodity users now do. Strategic reserves are still held for specific purposes, notably oil and grain, but with the stated aim of covering a supply emergency rather than of managing a price. Direct payments to producers when prices fall support incomes without touching the market price. And export restrictions during shortages remain common and generally make the world price worse.

The clearest case is the International Tin Agreement, which operated a store and a price band for decades and collapsed suddenly in October 1985. The controlling body had been supporting a price above the market for years while new supply grew outside the agreement, funding the purchases with borrowing, and when it could no longer pay it simply stopped, defaulting on very large obligations to banks and brokers. Trading in tin on the London Metal Exchange was suspended for four years and the price fell by more than half. The episode ended serious international enthusiasm for these schemes and produced years of litigation over who was liable.

Buying below a floor and selling above a ceiling can hold a commodity price inside a band while a physical store absorbs the swings, given storage, capital and a band near the true long-run average. Producers set the band and set it too high, so the scheme buys forever and runs out of money. The International Tin Agreement collapsed in 1985, suspending trading for four years.