What Moves Commodity Prices? Supply, Demand, Inventories and Interest Rates
5 min read · Public
A practical framework for understanding commodity moves, from physical availability and stocks to expectations, currencies and positioning. Includes a worked supply-and-demand example.
The short answer
Commodity prices respond to changes in expected scarcity, the cost of carrying supply through time and the willingness of participants to hold risk. Supply and demand are the foundation, but inventories, location, quality, timing, currencies and market positioning determine how that foundation translates into a traded price.
A useful explanation connects a new observation to a specific mechanism. “Supply concerns” is too vague. “A disruption reduces the amount deliverable before the nearby contract expires” is a clearer claim that can be investigated. This guide offers a repeatable framework, with hypothetical examples rather than current forecasts.
Supply is a flow and stocks are a buffer
Production measures how much is produced over a period. Inventory measures how much is held at a point in time. A market can consume more than it produces for a period by drawing down stocks. Conversely, strong production does not guarantee immediately available supply if transport, processing or quality requirements intervene.
For cocoa, arrivals describe beans reaching ports within a reporting period. They are not identical to national production or global inventory. Exchange warehouse stocks represent a particular location and coverage, rather than every bean available worldwide.
Suppose an illustrative commodity begins a year with 1.00 million tonnes in stock. Production is 4.80 million tonnes and use is 5.00 million tonnes. Ignoring other adjustments, the 0.20 million-tonne shortfall is met from inventory, leaving 0.80 million tonnes.
Simplified balance
Million tonnes
Opening stock
1.00
Production
4.80
Use
5.00
Production minus use
-0.20
Closing stock
0.80
This is a global teaching example, not a complete official balance. National balances also need imports and exports; statistical coverage and adjustments matter. At a global level, simply adding all imports to production without accounting for exports would double count trade.
The stocks-to-use ratio in this example is 0.80 ÷ 5.00 = 16%. It describes the scale of the remaining buffer relative to annual use. It does not tell you whether those stocks meet a particular delivery specification or when holders will offer them for sale.
Demand is more than the headline price
Consumption can change as buyers substitute, reduce use, reformulate products or draw down their own stocks. Some responses take time because recipes, equipment and contracts cannot be changed overnight. High prices can therefore coexist with apparently steady demand before a later adjustment becomes visible.
In cocoa, grindings measure processing activity rather than chocolate purchases at the till. A quarterly processing change should be interpreted with seasonal patterns, regional coverage and processor inventories in mind. Avoid treating one regional report as a complete global demand result.
A tonne available now is not always equivalent to a tonne promised months later. Storage, financing, insurance and the value of immediate availability contribute to differences between delivery months. Transport bottlenecks can also leave a local market tight while another holds ample stocks.
A futures curve in contango has later contracts above nearby contracts; backwardation describes the reverse. These are observable price relationships, not automatic guarantees about a future spot price. A curve can reflect several influences, including carry costs and delivery conditions.
The rollover guide explains why moving between contracts can change a chart quote without creating a free profit.
Expectations explain surprising reactions
Suppose traders expected production to fall 10%, but a new estimate suggests a 4% decline. Production is still lower, yet the news is less restrictive than expected. Prices could fall as some previously priced shortage risk is removed.
The correct comparison is therefore not only “higher or lower than last year”. It also includes “different from the credible expectation already held”. Where a sourced consensus is unavailable, say so. It is better to identify an uncertain baseline than invent what “the market expected”.
Currencies and interest rates add another layer
Exchange-rate changes alter local purchasing costs and the translated value of trading results. Interest rates influence financing and broader spending conditions. These mechanisms can pull in different directions across commodities and over different horizons.
The Federal Reserve explains how policy affects financial conditions and spending through interest rates. That transmission provides context; it does not establish a fixed immediate response for every commodity.
A crowded position may make a market sensitive to disappointing news. Short covering can accelerate a rally; liquidation can accelerate a decline. But a price move alone does not identify which participants acted, and aggregate positioning data can arrive with a delay.
Use COT data as a dated snapshot. Changes in gross longs and shorts are more informative than assuming every change in the net number has the same cause. Commercial hedging should not automatically be read as a directional recommendation.
A reusable evidence checklist
Define the commodity, contract, unit and observation time.
Identify what changed in supply, use or accessible stocks.
Separate new facts from forecasts and repeated reporting.
Compare with the previous estimate and any sourced expectation.
Check the relevant delivery period, currency and positioning context.
Record competing explanations and the next evidence to watch.
The EIA’s oil framework is a useful primary-source example of separating production, consumption, inventories and financial influences. It is oil-specific; do not copy every relationship directly into cocoa.
Practice by writing a two-sentence explanation for a move: first the observed change, then the mechanism you think connects it to price. Add one sentence stating what would disprove that mechanism.
Published research and personal commentary, not personalised investment advice. Trade ideas can fail; evaluate the assumptions and dated follow-ups. The original published post is preserved.