Commodities — Gold, Oil, Wheat

What a Commodity Actually Is

A commodity is a raw, physical good that's essentially interchangeable regardless of who produced it. A barrel of Brent crude oil pumped in the North Sea is, for trading purposes, the same as a barrel of Brent crude pumped anywhere else meeting the same specification. A bushel of wheat graded to a given standard is the same whether it was grown in Lincolnshire or Kansas. This interchangeability — economists call it "fungibility" — is exactly what allows commodities to be traded on global exchanges with a single quoted price, unlike, say, a house or a piece of art, where every unit is unique.

This is also what makes commodities fundamentally different from every other asset class covered elsewhere in this course. A share represents a claim on a company's future profits. A bond represents a loan that pays you interest. A commodity represents neither — it's simply a physical thing, and your return depends entirely on whether someone else is willing to pay more or less for that physical thing in the future than you paid today. Gold does not pay a dividend. Oil does not pay a coupon. Wheat does not compound. There is no underlying cash flow to value, no earnings report, no management team making decisions on your behalf. The entire return is price appreciation (or depreciation), full stop.

And yet commodities have mattered to human wealth for longer than any other asset class discussed in this course. Gold has been used as a store of value for roughly five thousand years, long before the first company share or government bond existed. Grain reserves were a measure of a civilisation's wealth and survival before money as we know it existed at all. Understanding why physical goods with no yield have held value for millennia — and how to access that value sensibly today without a warehouse — is what this chapter covers.

Hard Commodities vs Soft Commodities

Commodities are typically split into two broad families, and the distinction matters because they respond to very different forces.

Hard commodities tend to have longer, slower supply cycles — opening a new copper mine or oil field takes years of capital investment, so supply can't respond quickly to a demand spike, which is part of why energy and metals prices can swing dramatically when demand shifts unexpectedly. Soft commodities have faster supply cycles tied to a single growing season, but that same season is entirely at the mercy of weather — a drought in a major wheat-growing region can send global prices up sharply within months, while a bumper harvest can crash them just as fast.

Why Something With No Yield Holds Value

It's a fair question: if gold pays no dividend and sitting on a bar of it for ten years produces no income whatsoever, why has it held value across every currency collapse, war, and economic crisis in recorded history? The answer is that gold's value doesn't come from productive use — it comes from scarcity, durability, and universal recognition. There is a finite amount of gold that has ever been mined (roughly 212,000 tonnes by most estimates, with new mining adding a small percentage each year), it doesn't corrode or degrade, and it's recognised as valuable in essentially every culture and economy on earth. Those three properties together make it a credible place to park wealth when you don't trust a currency, a bank, or a government to hold that value for you instead.

Other commodities hold value for a more straightforward reason: the world genuinely needs them to function. Oil powers transport and manufacturing. Copper is essential to electrical wiring and, increasingly, to the renewable energy transition and electric vehicles. Wheat and corn feed billions of people. Their value isn't speculative in the way gold's partly is — it's tied directly to ongoing, measurable physical demand that doesn't disappear even when financial markets are in turmoil.

What all commodities share is that their price is set purely by supply and demand, with no earnings report or interest payment to anchor a "fair value" calculation the way a stock or bond has. This is precisely why commodities are harder to value using the tools used elsewhere in investing, and why commodity prices can detach from what might seem like a sensible level for extended periods in either direction.

This is also why commodities are sometimes described as having a "cost of carry" rather than a yield — holding a physical commodity, or a futures position tracking one, typically involves ongoing costs (storage, insurance, financing the position) rather than ongoing income. For gold held physically, this might be the cost of a vault or safety deposit box; for a futures-based oil position, it's the roll cost mechanics covered later in this chapter. These carrying costs are a quiet but persistent drag on returns that doesn't exist for a dividend-paying share or an interest-bearing bond, and they're part of why commodities, as an asset class, need a genuine price appreciation story to be worth holding at all — there's no income cushion if the price simply goes nowhere for years.

Gold in Depth: The Inflation Hedge Argument, Examined Honestly

Gold is the commodity most commonly discussed as a portfolio holding, usually under the banner of "inflation hedge" or "safe haven." Both claims are partly true and frequently oversimplified, and it's worth separating the honest version from the marketing version.

Over very long periods — multiple decades — gold has broadly kept pace with inflation, which makes sense given that it can't be printed or diluted the way a currency can. But "broadly kept pace over decades" is a very different claim from "reliably protects you during any given inflationary period," and the medium-term record is much messier. Gold fell for roughly two decades from its early-1980s peak even as inflation remained a live concern through parts of that period. More recently, gold performed well during the 2020–2022 period of rising inflation, which reinforced the inflation-hedge narrative for a new generation of investors — but it's worth remembering that correlation over one cycle doesn't prove a reliable mechanical relationship.

Gold also tends to do well during genuine crisis periods — banking stress, major geopolitical shocks, a sudden loss of confidence in a currency or government — because investors around the world reach for the same small set of assets perceived as safe when everything else feels uncertain. This "flight to safety" effect is reasonably well documented and is probably the most reliable of gold's supposed properties, even if it's impossible to predict exactly when the next crisis-driven rally will happen.

Most sensible portfolio frameworks suggest holding gold, if at all, as a modest allocation — commonly cited in the 5–10% range — rather than as a core holding or a replacement for a diversified equity and bond portfolio. Think of it as portfolio insurance: something you're generally happy to hold a small amount of and mostly ignore, that may do very little for long stretches, but that has a decent historical record of holding up or rising during the specific kind of crisis when almost everything else is falling.

Oil and Energy: A Different Kind of Commodity

Oil behaves nothing like gold, and conflating the two is a common beginner mistake. Where gold's demand is largely about sentiment and store-of-value behaviour, oil's demand is overwhelmingly industrial and immediate — transport, manufacturing, heating, plastics. This means oil prices respond sharply and quickly to real-world supply disruptions (a war in a major producing region, an OPEC+ production cut decision, a hurricane shutting down US Gulf Coast refineries) and to genuine shifts in global economic activity, since oil demand rises and falls with how much the world's factories, planes, and lorries are actually running.

The 2020 pandemic produced one of the strangest moments in commodity market history: oil demand collapsed so suddenly and so completely, with planes grounded and factories shut, that US crude oil futures prices briefly went negative — producers were effectively paying buyers to take oil off their hands because storage capacity had run out. This is a useful reminder that commodity prices, unlike a share price, can be influenced by genuinely physical constraints (how much storage exists, how much a pipeline can carry) that have no equivalent in financial markets.

Energy transition dynamics add a longer-term layer of uncertainty specific to oil and natural gas that doesn't apply to most other commodities: the long-term demand trajectory for fossil fuels is genuinely contested, with some forecasts expecting continued growth for decades and others expecting a meaningful decline as renewable energy and electric vehicles scale up. This long-term uncertainty is part of why energy commodity investments carry a different risk profile to, say, copper, which benefits from many of the same electrification trends that are expected to reduce oil demand.

Agricultural Commodities: Weather Is the Market

Soft commodities — wheat, corn, coffee, sugar, soybeans — are driven more directly by weather and growing conditions than almost any other asset class covered in this course. A drought across a major wheat-exporting region, a frost that damages a coffee harvest in Brazil, or a flood that delays planting can move global prices meaningfully within a single season, because unlike a mine or an oil well, a failed harvest simply cannot be replaced until the next growing cycle comes around.

Global trade and geopolitics add a second layer on top of weather. Russia and Ukraine together account for a very large share of the world's wheat and sunflower oil exports (roughly a quarter to a third of global wheat exports between them in a typical year, though this shifts), which is why the 2022 invasion of Ukraine caused an immediate, sharp spike in global wheat prices — a geopolitical event directly disrupting a physical food supply in a way that has few parallels in other asset classes. Export bans, introduced by some governments during periods of food insecurity to protect domestic supply, can compound these price spikes further by removing supply from the global market precisely when it's most needed elsewhere.

For retail investors, agricultural commodities are generally the hardest of the three broad categories (precious metals, energy, agriculture) to access sensibly and the least commonly recommended as a standalone holding, for reasons covered in the next section — they're almost exclusively accessed through futures-based products that carry structural costs most investors don't fully appreciate going in.

A further complication specific to agricultural commodities is that many of them don't trade as a single, simple global price the way gold or oil broadly do. Wheat, for example, has distinct regional varieties and grades (hard red winter wheat, soft red winter wheat, and others) that can trade at meaningfully different prices depending on protein content, growing region, and intended use, which makes a single "wheat price" a simplification useful for headlines but less precise than the gold or oil price quotes that dominate financial news. This added complexity is one more reason most retail investors are better served getting agricultural exposure indirectly, through a diversified fund or through food and agriculture company shares, rather than attempting to trade a specific grain or soft commodity directly.

How to Actually Access Commodities Without a Warehouse

You are not going to take physical delivery of a tanker of crude oil or a silo of wheat, and you shouldn't want to — storage, insurance, and spoilage costs make direct physical ownership impractical for anything other than precious metals. There are four realistic routes in, each with a different risk and cost profile.

For the large majority of retail investors wanting sensible, low-effort commodity exposure, a physically backed gold ETF (for precious metals specifically) or a diversified commodity index ETF (for broader exposure) covers the overwhelming majority of use cases without needing to touch futures contracts, physical storage logistics, or individual company analysis.

The Hidden Cost Most People Miss: Contango and Roll Costs

This is the single most important technical point in this chapter, and it's the reason many investors who buy an "oil ETF" expecting it to simply track the oil price end up disappointed with their returns even when oil itself has risen. Most commodity ETFs that aren't backed by physically stored metal — oil, gas, and agricultural ETFs in particular — don't hold the physical commodity at all. They hold futures contracts, and because a futures contract has an expiry date, the fund must continuously sell the contract about to expire and buy a new one further out, a process called "rolling."

When futures contracts for later delivery dates are priced higher than contracts for near-term delivery — a market condition called "contango," which is the normal state for many commodities most of the time — this rolling process means the fund systematically sells low and buys high every single month, bleeding value even if the spot price of the underlying commodity doesn't move at all. Over a period of years, this roll cost can meaningfully erode returns relative to simply tracking the headline commodity price, and it's a cost that doesn't show up clearly in a simple price chart comparison unless you know to look for it.

This is exactly why energy company shares or a diversified energy sector ETF are often a more practical way to get oil-related exposure for most retail investors than a dedicated oil futures ETF — you're buying a company that profits from producing and selling oil (and that pays you a dividend along the way), rather than a financial instrument with a structural cost built into how it tracks the price.

Commodities' Role in a Diversified Portfolio

The case for holding any commodities at all in a long-term portfolio rests on diversification rather than on expected returns, and it's worth being precise about that distinction. Over very long periods, broad commodity indices have historically delivered lower real returns than equities — there's no earnings growth or compounding mechanism driving commodity prices higher the way there is for a diversified portfolio of profitable, growing companies. What commodities offer instead is a return pattern that, at times, moves differently from stocks and bonds — rising during periods of unexpected inflation or geopolitical shock when both stocks and bonds may be struggling, which is precisely when a diversifying asset is most valuable.

This diversification benefit is genuine but inconsistent — it shows up clearly during some periods (the 2021–2022 inflation surge, for instance, when commodities broadly outperformed both stocks and bonds) and is much weaker or absent during others. A sensible allocation framework treats commodities, including gold, as a minority diversifying position rather than a return-driving core holding — most frameworks suggest somewhere in the 0–10% range depending on how much an investor specifically values inflation protection versus simply accepting that a well-diversified global equity index fund already provides indirect, modest exposure to commodity-linked sectors through its energy, mining, and agricultural company holdings.

UK Tax Treatment

Commodity ETFs and mining/energy shares are taxed the same way as any other investment fund or share for UK investors: gains are subject to Capital Gains Tax when sold outside a tax-advantaged wrapper, and any dividends from mining or energy company shares are taxed under the normal dividend tax rules. Held inside a Stocks and Shares ISA or a SIPP, both gains and dividend income are sheltered entirely, which makes the ISA the sensible default home for commodity exposure exactly as it is for most other investments covered in this course.

Physical gold held directly (coins and bars, rather than through an ETF) has a specific UK quirk worth knowing: certain UK legal tender gold coins — Britannias and Sovereigns specifically — are exempt from Capital Gains Tax entirely, because legal tender currency is generally outside the scope of CGT. This is a genuine, legal advantage unique to physical gold in these specific coin forms and doesn't apply to gold bars, most foreign coins, or gold held through an ETF, where normal CGT rules apply as usual.

Industrial Metals: "Dr. Copper" and the Economic Cycle

Copper occupies an interesting middle ground between the precious metals covered above and the broader industrial commodity complex, and traders have nicknamed it "Dr. Copper" for a specific reason: because copper is used so extensively across construction, electrical wiring, and manufacturing, its price has historically been treated as an informal barometer of global economic health — rising when industrial activity and construction are expanding, falling when a slowdown is underway, often ahead of other economic data confirming the same trend.

Copper, along with lithium, nickel, and cobalt, has taken on an additional layer of importance in recent years because of its central role in the renewable energy transition — electric vehicles use roughly four times as much copper as a comparable petrol car, and wind turbines and solar installations are copper-intensive relative to traditional power generation. This has led some analysts to argue that structural demand for these specific industrial metals will grow for decades regardless of the usual economic cycle, though it's worth treating any long-range structural demand forecast with some scepticism — commodity markets have a long history of supply eventually responding to sustained high prices through new mining investment, which can undercut even well-reasoned long-term demand theses.

For retail investors, industrial metals exposure is most commonly accessed through diversified mining company shares or a broad metals and mining sector ETF, for the same roll-cost reasons that make futures-based products a poor fit for most individual investors, as covered in the contango section above.

Why Commodities and the US Dollar Are So Closely Linked

Most globally traded commodities — oil, gold, copper, and most agricultural staples — are priced in US dollars on international markets, a legacy of the dollar's role as the world's primary reserve and trade-settlement currency. This creates a mechanical link between the dollar's strength and commodity prices that catches many newer investors by surprise: when the dollar weakens against other currencies, commodities priced in dollars tend to become cheaper for buyers using other currencies, which increases demand and tends to push the dollar price higher; when the dollar strengthens, the opposite tends to happen.

This relationship is why commodity investors often watch US Federal Reserve policy and the US Dollar Index almost as closely as they watch supply and demand data for the specific commodity itself. A Federal Reserve interest rate decision, even one with no direct connection to oil supply or gold mining output, can move commodity prices through this currency channel alone. It's a useful reminder that commodities, despite being physical goods, are deeply embedded in the global financial and currency system, not insulated from it.

Commodity Supercycles: Why These Markets Move in Decade-Long Waves

Commodity markets have a well-documented tendency to move in extended, multi-year or even multi-decade waves known as "supercycles," driven by the mismatch between how quickly demand can shift and how slowly supply can respond. A sustained surge in demand — China's rapid industrialisation through the 2000s is the textbook modern example, pulling in enormous quantities of copper, iron ore, and oil as the country built infrastructure and manufacturing capacity at an extraordinary pace — pushes prices up for long enough that producers eventually commit the years of capital investment needed to open new mines or oil fields. By the time that new supply finally arrives, demand growth has often slowed, and the market swings from shortage to surplus, pushing prices down for years until the cycle eventually repeats in the other direction.

Understanding this pattern is useful context for interpreting any commodity price chart you look at: a price that looks "cheap" relative to recent history may simply be mid-cycle in a multi-year downswing with further to fall, and a price that looks "expensive" may still have room to run if the underlying supply response hasn't caught up yet. This is a meaningfully different dynamic from how equity markets tend to behave, where company-specific earnings growth provides a more continuous, less wave-like underlying driver of long-term value.

The 1970s Case Study: Commodities During Stagflation

The clearest historical example of commodities earning their place in a diversified portfolio is the 1970s, a decade that combined high inflation with weak economic growth — a combination now commonly called "stagflation." Equity markets struggled badly in real (inflation-adjusted) terms through much of the decade, while oil prices surged dramatically following the 1973 OPEC oil embargo and the 1979 Iranian revolution, and gold rose from roughly $35 an ounce (fixed under the Bretton Woods system until 1971) to several hundred dollars by the decade's end once it was allowed to float freely.

This period is frequently cited as the strongest historical case for holding commodities specifically as insurance against the scenario where both stocks and bonds struggle at once — a genuinely plausible scenario (rising inflation forcing interest rates up, which hurts bond prices, while simultaneously squeezing corporate profit margins and consumer spending, which hurts equities). It's worth being clear-eyed, though, that the 1970s was a particularly severe and specific set of circumstances, including a genuine global energy supply shock, and it would be a mistake to assume every period of elevated inflation produces the same pattern — the 2021-2022 inflationary period, for comparison, saw a much more mixed picture across different commodities, as covered earlier in this chapter regarding gold's uneven relationship with rate hikes.

Common Mistakes

Buying a futures-based commodity ETF expecting it to simply track the spot price. As covered above, contango-driven roll costs can cause significant long-term underperformance relative to the headline commodity price. Check the fund's structure before buying.

Treating gold as a growth investment rather than insurance. Gold has long stretches — sometimes a decade or more — of flat or negative real returns. Sizing a gold position as if it were a core growth holding, rather than a small diversifying position, usually leads to disappointment.

Confusing a mining or energy company's share price with the commodity price itself. A mining company's shares are affected by the metal price, but also by its own debt levels, operational problems, and management decisions — a well-run company can outperform a falling commodity price, and a badly run one can underperform a rising one.

Overweighting commodities after a strong run. Commodity cycles tend to be long and can reverse sharply once a supply response catches up with elevated demand — chasing recent strong performance is a particularly common mistake in this asset class.

Ignoring storage and security for physical holdings. Physical gold and silver require real consideration of insurance and secure storage, costs that reduce the net return and are easy to underestimate when first buying.