Commodity ETPs and Contango Drag
Why a commodity fund can lose money over years even while the commodity's spot price is flat or rising, because the fund holds futures contracts, not the physical commodity, and has to keep rolling them forward.
Prerequisites: Contango and Backwardation, Roll Yield
Most commodity ETPs don't hold barrels of oil or bushels of wheat sitting in a warehouse — storing and insuring physical commodities at scale is impractical for most, so instead the fund holds futures contracts on the commodity and continually rolls them forward as each contract nears expiry: selling the contract about to expire and buying the next month out. That rolling process is where an entire, separate source of return or loss comes from, on top of whatever the spot price of the commodity itself does.
When a futures curve is in contango — longer-dated contracts priced higher than near-dated ones, the normal state for a commodity that's costly to store — the fund is systematically selling low (the expiring contract) and buying high (the next one out) every time it rolls. That gap is a real cost paid every month, called roll drag, and it can accumulate to a meaningful negative return over a year even if the spot price of the commodity is unchanged or has actually risen a little. The reverse situation, backwardation, works in the fund's favor: rolling from a higher-priced near contract into a cheaper further-dated one is a small tailwind, added on top of whatever spot does.
This is the single most common reason retail investors are surprised by a commodity ETP's long-run performance: many oil and natural gas futures markets have spent long stretches in contango, so a fund tracking "oil" can post a materially worse multi-year return than the oil spot price headline they were watching, purely from the mechanical cost of rolling contracts forward month after month.
Some funds try to soften this by spreading their futures exposure across several contract months rather than always holding the single nearest-to-expiry contract, which can reduce (but not eliminate) the roll-drag effect during persistent contango, at the cost of a slightly less precise short-term tracking of the front-month spot price. Reading a commodity ETP's prospectus for which specific contracts it holds and how it rolls them is worth the effort before assuming its return will simply mirror the commodity price seen in the news.
Most commodity ETPs hold rolling futures contracts, not the physical commodity, so their return combines the spot price move with a separate roll effect: contango (upward-sloping futures curves) creates a persistent roll drag that can make fund returns lag the spot commodity for years, while backwardation works the other way. Always check the shape of the futures curve, not just the spot price, before judging a commodity ETP's long-run performance.
Further reading
- Erb & Harvey, The Strategic and Tactical Value of Commodity Futures