Commodities

Commodities are interchangeable raw materials that markets price as a class of investable assets. They fall into three broad groups: energy (crude oil, natural gas, gasoline), metals (industrial metals such as copper and aluminum, and precious metals such as gold and silver), and agriculture (grains, livestock, and "softs" such as coffee, sugar, and cotton). A barrel of a given grade of oil is a barrel of that oil regardless of who produced it, and that fungibility is what lets commodities trade on standardized exchanges.

As an investment, a commodity is fundamentally different from a stock or a bond, because it generates no cash flow. A share can pay a dividend and a bond pays interest, but a commodity just sits there. The whole return, positive or negative, is the change in its price, minus whatever it costs to store, insure, or maintain exposure. That single fact drives most of what is distinctive about investing in the class.

Very few investors take physical delivery. Direct ownership of the goods means storage, insurance, and spoilage or security costs, so households almost always gain exposure through financial instruments instead. The main routes are futures contracts, which are agreements to buy or sell a commodity at a set price on a future date, and commodity funds. Exchange-traded funds and exchange-traded notes package that exposure into a share bought in a brokerage account; some hold physical metal, but many hold futures, which introduces a cost most buyers do not expect.

That cost is the roll. A futures-based fund must sell contracts as they near expiration and buy later-dated ones to stay invested. When later-dated contracts cost more than expiring ones, a condition called contango, each roll sells low and buys high, and the fund bleeds value even if the commodity's spot price is flat. The opposite condition, backwardation, works in the fund's favor. Over long holding periods, roll costs can cause a commodity fund's return to diverge substantially from the change in the headline spot price.

The inflation-hedge argument is the usual reason commodities appear in a portfolio, and it deserves a careful statement rather than a slogan. Commodity prices are a direct input to consumer prices, so the class has some tendency to rise with inflation, and energy in particular has shown that relationship. But the connection is inconsistent: it varies by commodity and by episode, and the volatility of commodities is high enough that the hedge can be swamped by ordinary price swings. Specific sub-topics have their own pages: gold as an investment is covered separately, as is the mechanics of holding physical metals inside a retirement account.

An investor who wants commodity exposure typically buys a fund or, less commonly, trades futures directly. A broad-basket commodity ETF spreads exposure across energy, metals, and agriculture; a single-commodity fund tracks one market. The fund's value tracks the underlying prices, adjusted for roll costs when it holds futures and for fund expenses.

A hypothetical example of contango's drag. Suppose a fund holds oil futures expiring next month priced at $80, while the contract for the following month costs $82. To stay invested, the fund sells at $80 and buys at $82. If the spot price of oil is unchanged when that later contract nears expiration, the fund has still paid $2 more per barrel of exposure to roll forward, a 2.5 percent cost baked in before any price move. Repeated month after month in a persistent contango, that drag can leave a futures-based fund well behind a flat spot price.

Pros

• Potential diversification, because commodity prices are driven by supply and demand for physical goods rather than by corporate earnings.
• Some inflation sensitivity, especially in energy, that stocks and bonds lack.
• Easy access through exchange-traded funds without the burden of storing physical goods.

Cons

• No income at all: the entire return is price change minus holding costs.
• Futures-based funds can lose value to contango even when spot prices are flat.
• High volatility, so the diversification and inflation-hedge benefits can be overwhelmed by ordinary price swings.
• The tax treatment of commodity funds varies by structure and can be complex, including the higher collectibles rate for physical precious-metal funds.