Why does the Australian dollar trade like a commodity?
Some currencies co-move with the price of what their country digs up or pumps out. The mechanism is real and economically well founded — and the correlation is far less reliable than the nickname "commodity currency" suggests.
The mechanism: terms of trade
A country's terms of trade is the price of its exports relative to the price of its imports. When export prices rise, the same physical exports buy more imports; national income rises without anyone working harder.
For a commodity exporter that chain runs: export price up → export revenue and national income up → domestic demand and often inflation up → the central bank leans tighter → the interest differential widens → the currency appreciates. Note that the last link is the rate differential from Unit 1 — the commodity story is not an alternative to the rates story, it is one of the things that drives the rates story.
The usual suspects
- AUD — iron ore, coal and LNG, with China as the dominant buyer. Australia's currency is as much a proxy for Chinese industrial demand as for commodities as such.
- CAD — crude oil, though the linkage is diluted by an enormous, mostly non-energy trade relationship with the United States.
- NOK — Brent crude and gas. Norway is the instructive case: its sovereign wealth fund deliberately insulates the domestic economy from oil revenue, so the transmission is weaker than you would expect, while NOK's relatively thin liquidity makes it move more than you would expect.
- Also NZD (dairy), CLP (copper), ZAR and BRL (metals and softs).
A worked illustration
Take a rounded, illustrative case. An economy exports 900 million barrels of oil a year. The price falls from $100 to $60:
900,000,000 × 40 = $36 billion a year of lost export revenue
Against a $2 trillion economy, that is about 1.8% of GDP removed from national income in one step. That is a large macroeconomic shock, and it is why the currency response to a sustained commodity move is not sentiment — it is arithmetic about income.
The historical episode: Brent fell from around $115 in June 2014 to around $28 in January 2016. Over roughly that window USD/CAD moved from about 1.06 to about 1.46 — a Canadian dollar depreciation of close to 30% — and the Norwegian krone weakened substantially against the dollar as well.
Three reasons not to trust the correlation
It breaks when rates dominate. Through 2021–2022 iron ore prices were historically strong for extended stretches while the Australian dollar weakened, because the Federal Reserve was tightening faster than the Reserve Bank of Australia. The rate channel and the terms-of-trade channel pointed in opposite directions, and the rate channel won.
It ignores the difference between price and income. On 20 April 2020 the expiring WTI futures contract settled at −$37.63 a barrel. The Canadian dollar did not collapse, and it should not have: the negative print was a storage and contract-expiry mechanic in one instrument, not a change in the price Canada actually realised on its exports. A commodity currency responds to the terms of trade, not to a futures curve artefact.
The causation runs both ways. Most commodities are priced in dollars, so a stronger dollar mechanically depresses dollar commodity prices. Some of the observed "commodity currency" correlation is just the dollar, appearing on both sides of the comparison.
The disciplined version
A commodity currency is a currency whose national income is unusually sensitive to one price. That is a statement about the economy's structure. It is not a promise about correlation on any particular day, and it is certainly not a basis for expecting one asset to follow another. Nothing here is a forecast or advice.
In the data
The two sides of the comparison run on different calendars. The physical crude price below comes once a month, stamped on the first day, 471 months of it for Brent.
A currency pair prints every day, and for the Australian dollar that now includes Saturdays and Sundays, while the crude futures on the chart below print Monday to Friday only (both checked 29 September 2026). Line them up day by day and the currency's weekend rows have no oil price to pair with, so they either vanish or inherit Friday's number depending on how the two were matched. A correlation computed that way is measuring the matching as much as anything about the currency.
Try it now
- The Australian dollar and crude oil, over the longest window this page holds, are below. Switch both to Monthly. You are looking for the stretches where the two lines bend at the same time — and there are more of them than a currency chart has any obvious right to.
- Measure one multi-year stretch where they moved together and one where they clearly did not. Write both percentage pairs down. Australia does not export oil in quantity, so what you are seeing in the first stretch is the commodity cycle, not the barrel.
- For the stretch where they diverged, the usual competitor is the interest-rate channel: a central bank moving on inflation rather than on terms of trade. Write one neutral sentence on what was competing with the commodity channel, and note that you cannot tell from a price chart alone which one won.