Commodity Currencies (AUD, CAD, NZD): Terms of Trade Explained

Commodity currencies are currencies that move with the world prices of the goods their countries export. The Australian dollar, Canadian dollar, and New Zealand dollar are the three established commodity currencies in the G10, and their FX behaviour is fundamentally linked to a concept called terms of trade — the ratio of what a country earns on its exports relative to what it pays for its imports. When terms of trade improve, national income rises and the currency tends to follow.

What is terms of trade?

Terms of trade (ToT) is the ratio of a country's export price index to its import price index, typically expressed as an index relative to a base year. A rising ToT means the country gets more imports for the same amount of exports — its purchasing power in international trade improves.

For commodity exporters, ToT swings are large because commodity prices are volatile. When iron ore doubles, Australia's ToT surges. When oil collapses (as in 2014–16), Canada's ToT plunges. These swings flow through to national income, government revenues, corporate profits, and ultimately — via capital flows and purchasing power — into the currency.

The formal academic grounding for this mechanism comes from Yu-chin Chen and Kenneth Rogoff's paper "Commodity Currencies", published in the Journal of International Economics, Vol. 60, No. 1, 2003, pp. 133–160. Chen and Rogoff studied the Australian, New Zealand, and Canadian dollars and found that world commodity export prices are a strong and robust driver of their real exchange rates — a finding that held even after controlling for interest-rate differentials, relative price levels, and other standard macro fundamentals. Critically, they found the relationship works in the causal direction: commodity prices → exchange rates, not the reverse — meaning commodity prices function as exogenous terms-of-trade shocks that feed into FX, rather than FX driving commodity prices.

The Australian dollar: iron ore and China

Australia's primary commodity driver is iron ore. With A$124.5 billion in annual iron ore export revenue (2023–24) representing roughly a fifth of the nation's total exports, and China buying about 85% of that output, the AUD is deeply sensitive to Chinese steel demand and global iron ore pricing.

The AUD/iron ore spot correlation is approximately 0.88 — one of the strongest commodity-currency relationships in FX markets. When iron ore prices surged above $200 per tonne in 2021 on the back of Chinese post-COVID infrastructure stimulus, AUD rallied sharply. When iron ore fell below $100 per tonne during China's property-sector crisis in 2023, AUD gave back much of those gains despite the RBA being in an active hiking cycle.

For a full breakdown of the China-AUD transmission chain including the yuan and PMI dynamics, see the dedicated AUD China proxy post. For a currency-page view of where AUD scores right now, visit /currency/aud.

The Canadian dollar: black gold and the Loonie

Canada's primary commodity is crude oil and bitumen. The energy sector accounts for approximately 10% of Canadian GDP, and petroleum products represent the country's largest single export category at roughly 16% of total exports. The Canadian dollar — nicknamed "the Loonie" — has one of the most studied oil-price correlations in commodity FX research.

Bank of Canada research models suggest that a sustained $10-per-barrel increase in oil prices typically strengthens the Canadian dollar by approximately 1.5–2% against the US dollar and adds about 0.4% to Canada's GDP growth. The WTI crude / USD-CAD correlation measured over rolling 30-day windows has been as strong as −0.78 (strong inverse: higher oil = stronger CAD = lower USD/CAD).

The CAD-oil relationship is more complex than it appears, however. Canada's oil production (primarily Alberta oil sands) is landlocked — it reaches refineries via pipeline, not deepwater tanker — and the infrastructure constraints mean the Canadian heavy crude blend (Western Canadian Select) often trades at a significant discount to WTI. That discount can decouple CAD from the headline WTI move. The Bank of Canada has also noted that the CAD has become somewhat less purely "petro-currency" over time as Canada's service and tech sectors have grown relative to energy.

The New Zealand dollar: dairy, soft commodities and China

New Zealand's primary commodity exposure is to agriculture, particularly dairy. Dairy products account for approximately 34% of New Zealand's merchandise exports and an estimated 5.6% of national GDP in 2024, according to the US Department of Agriculture and Statistics New Zealand. The Fonterra cooperative is New Zealand's single largest company by revenue and its GlobalDairyTrade (GDT) auction prices — published fortnightly — are closely watched as leading NZD indicators.

NZD also has a China exposure story similar to (but less concentrated than) AUD's: China is New Zealand's largest export destination for both dairy and meat, accounting for over 20% of total merchandise exports. A slowdown in Chinese consumer spending hits NZD via the dairy channel in the same way it hits AUD via iron ore.

The risk-sentiment overlay

All three commodity currencies share one additional characteristic beyond their commodity linkage: they are risk-sensitive. In periods of global growth optimism (risk-on), capital flows toward the higher-yield, higher-growth commodity currencies. In risk-off episodes — financial crises, recession scares, pandemic shocks — global investors sell commodity FX rapidly and rotate into safe havens (see the three safe havens post for the JPY/CHF/gold dynamic).

This means commodity currencies are priced by the intersection of two forces at all times: their commodity fundamentals and global risk sentiment.

When commodity prices are rising but risk sentiment is deteriorating — for example, oil higher on geopolitical supply shock but equities falling on recession fear — the two forces create opposing pressures on CAD and the currency often ranges. Divergence between the commodity and risk signals is a frequent source of whipsaws in commodity FX.

How the PIPTHEORY meter weights commodity exposure

The PIPTHEORY Macro Currency Strength Meter treats commodity terms-of-trade as one of five fundamental factors in its scoring model. For AUD, CAD, and NZD, the commodity factor carries substantial weight — reflecting the Chen-Rogoff finding that commodity prices are a robust, exogenous driver of these currencies. The risk-mood factor (risk-on/off) captures the sentiment overlay that modulates the commodity signal.

When both the commodity factor and the risk factor are pointing in the same direction for AUD, CAD, or NZD, the meter's score will be strongly positive or negative — and that confluence is typically when trends in commodity FX are most reliable. When they diverge, the score is muted and range-trading is the more likely environment.

You can compare where AUD, CAD, and NZD currently rank against the full G10 on the live meter, and read the methodology on the about page. For AUD specifically, the AUD China proxy post breaks down the iron ore channel in detail. The carry trade explainer covers how commodity currencies also interact with the interest-rate differential factor.

What happens when commodity cycles diverge

The three commodity currencies do not always move together. Their fortunes diverge when their respective commodity cycles are out of phase — which is common, because iron ore, crude oil, and dairy prices are driven by different supply and demand dynamics and do not always move in tandem.

During 2014–2016, oil prices collapsed from above $100 per barrel to below $30 — devastating CAD as Canada's trade balance deteriorated sharply. Over the same period, iron ore also fell, but the dairy cycle was more stable. NZD outperformed CAD by a wide margin during those two years because the supply shock was commodity-specific. The reverse occurred in 2021–2022: oil prices surged on post-COVID reopening and the Ukraine-related supply shock, lifting CAD strongly even as iron ore prices softened from their 2021 peak, meaning AUD and NZD lagged CAD during that stretch.

This divergence is why the PIPTHEORY meter scores each commodity currency individually against its own commodity basket, rather than treating all three as interchangeable. CAD's currency page, AUD's currency page, and NZD's currency page each reflect the commodity mix relevant to that specific economy.

Terms-of-trade booms and the Dutch Disease problem

One important nuance for long-term thinkers on commodity currencies is the concept economists call Dutch Disease — the phenomenon where a commodity export boom strengthens the currency so much that it makes the non-commodity tradeable sector (manufacturing, non-commodity exports) uncompetitive. The term originates from the Netherlands' experience following the discovery of North Sea natural gas in the late 1950s and 1960s, but the mechanism is universal to resource exporters.

For Australia, Canada, and New Zealand, terms-of-trade booms create a structural tension: the commodity sector benefits directly from higher export prices, but a rising currency simultaneously squeezes exporters in other sectors — tourism, education services, manufacturing — who earn foreign currency but face higher domestic costs when translated back. Central banks in all three countries monitor real effective exchange rates against this backdrop. The Reserve Bank of New Zealand has explicitly noted in its analytical work that commodity price booms lift the exchange rate in ways that offset a significant portion of the real income gain, tempering the boom's domestic impact.

This structural tension partly explains why commodity currencies display mean-reverting behaviour over longer cycles. The same terms-of-trade boom that drives the currency higher eventually creates competitive pressures that slow non-commodity growth, narrow the current-account surplus over time, and set up the next cycle of currency weakening when commodity prices normalise. Understanding this cycle is important context for any macro view on AUD, CAD, or NZD.

Educational macro context only — not investment advice.