Commodities in your portfolio

Commodities are raw materials — oil, natural gas, copper, wheat, corn, cattle. You can gain exposure through futures-based ETFs, commodity producer stocks, or broad commodity index funds. The case for owning them is nuanced: they provide inflation protection and diversification, but with significant drag in non-inflationary periods.

The diversification case

Commodities have historically low correlation with stocks AND bonds, which makes them a useful portfolio diversifier during specific environments — most notably, high and rising inflation. In 2022, when stocks and bonds both fell, commodities surged. Having even 5% in commodities meaningfully reduced portfolio pain that year.

The drag problem

Commodity futures suffer from 'contango' — where the futures price is higher than the spot price — which creates a persistent roll cost that eats into returns. Over long periods in normal inflation environments, a broad commodities fund tends to return near zero after inflation. You're paying for insurance that only pays off in specific environments.

The practical answer

Most portfolios don't need commodities. If you want them: 5% in a broad commodities index fund (DJP, PDBC, or GSG) is a reasonable allocation. Use it as an inflation hedge, not a growth engine. Rebalance into it when it's down (after inflationary periods cool) and trim it when it's up (after a spike). And don't touch leveraged commodity products — they decay rapidly and are designed to lose money for holders.

What is actually inside a commodities fund

The first row explains more portfolio behavior than most investors realize: a 'diversified' commodity index is often half an oil bet wearing a costume. When energy dominates the index, your commodity sleeve rises and falls with crude far more than with wheat or copper. If you want inflation insurance rather than an energy position, check the fund's sector weights — some products cap energy exposure, and the difference between a 30% and a 55% energy weight is the difference between a hedge and a leveraged opinion about OPEC.

The roll cost, in dollars

Here is the drag problem with actual numbers. Suppose spot oil sits at $80 and the futures contract three months out trades at $82 — a typical contango. A fund holding $10,000 of expiring contracts must roll into the more expensive ones, buying roughly 2.5% less exposure each quarter. If spot oil ends the year exactly where it started, the fund did not return zero — it lost something like 8-10% to the roll, minus whatever interest the collateral earned. This is why a commodity ETF can trail the headline commodity price by miles over multi-year holds, and why the products only shine when markets flip into backwardation, as they did during the 2021-2022 squeeze, when the roll briefly paid holders instead of charging them.

A worked example: the 2022 stress test

Consider two $500,000 portfolios entering 2022. The first is a plain 60/40; it finished the year down roughly 16-17%, about $83,000, as stocks and bonds fell together. The second carved 5% from each side into a broad commodity fund — 55% stocks, 35% bonds, 10% commodities. Commodities returned roughly +15-20% that year, and the blended portfolio lost about $70,000 instead. A $13,000 improvement in the exact scenario the sleeve exists for. The honest counterweight: over the preceding decade, that same 10% sleeve would have cost the portfolio roughly 0.5-0.8% of return per year while stocks compounded. Commodities are insurance with a visible annual premium — the question is never whether the premium exists, but whether the 2022-style protection is worth it to you.

Common mistakes

• Buying commodities AFTER the inflation spike makes headlines. The insurance pays when you owned it beforehand; 2023 buyers of 2022's winner learned this quickly.
• Using leveraged or single-commodity ETPs as long-term holdings. Daily-reset leverage decays mathematically; these are trading instruments with expiry dates on their usefulness.
• Assuming energy stocks are a commodities allocation. They correlate with the stock market most of the time — you already own them inside your index funds.
• Ignoring the tax treatment: many futures-based funds issue K-1 forms or mark positions to market annually. PDBC-style no-K-1 funds exist precisely to avoid this paperwork.
• Sizing the sleeve so large that its dead decades change your retirement math. At 5% a lost decade in commodities is a rounding error; at 25% it is a life decision.

If all of this sounds like more machinery than you want to maintain, that conclusion is respectable: TIPS, I bonds, and a globally diversified stock portfolio already carry meaningful inflation resilience for most savers, with none of the roll math. The commodity sleeve is an optional refinement for people who understand what they are buying — not a requirement for a well-built portfolio.

A final calibration on expectations: over the century-plus of available data, spot commodity prices have barely beaten inflation — technology keeps making extraction cheaper, which caps real prices over the long run. Whatever return a commodity fund delivers comes mostly from collateral interest and rebalancing across volatile, weakly correlated contracts, not from raw materials appreciating. That is a real but modest engine, and it is why the sober role for commodities is a 0-10% diversifier owned for its behavior in bad years — never a core holding owned for growth.

Whichever way you decide, decide once and put it in your investment policy: the target weight, the specific fund, and the annual rebalancing date. Commodity sleeves abandoned after three boring years and re-added after a spike deliver the worst of both worlds — all of the drag, none of the insurance payout, plus a trading record that embarrasses you at tax time.