iShares S&P GSCI Commodity-Indexed Trust (GSG)

The iShares S&P GSCI Commodity-Indexed Trust is an exchange-traded fund that tracks a broad index of commodity futures contracts — oil, natural gas, metals, and agricultural products. It exists because commodities themselves do not trade like stocks; they trade on specialist exchanges and in derivatives markets, and most individual investors cannot easily buy crude oil or wheat directly. GSG pools that complexity into a single, simple instrument. Since its inception in 2006, it has been among the largest commodity index funds available to retail investors, with assets regularly cycling between billions of dollars.

A commodity fund buys what most investors cannot: a basket of oil wells, grain silos, and metal vaults, all bundled into one share.

The fund is managed by BlackRock’s iShares division and tracks the S&P GSCI, a commodity index maintained by S&P Dow Jones Indices. The index itself holds roughly equal dollar weights across commodities in five groups: crude oil and refined products, natural gas, precious metals, industrial metals, and agricultural commodities like wheat, corn, and soybeans. At any given time, the fund holds futures contracts on most of those underlying commodities, rolling them over before they expire (a constant operational task in any commodity fund). It also holds cash and short-term investments while awaiting the next roll or rebalance.

How the mechanics work

Investors buy and sell GSG shares on a stock exchange just like any regular stock. BlackRock’s fund managers then use inflows and outflows to adjust the underlying commodity futures positions. When investors deposit cash to buy GSG shares, that money goes into buying or rolling commodity futures contracts. When they sell shares, the opposite happens — the fund liquidates futures to send cash back out. The fund is designed to track the S&P GSCI index as closely as possible, so its holdings shift whenever the index rebalances or the underlying contracts approach expiration.

This is where the real friction enters. Commodity futures expire on fixed dates, and the fund must sell the expiring contract and buy a newer one before expiration arrives. If near-term contracts trade at a lower price than the ones further out (a condition called contango), the fund is forced to sell cheap and buy dear, a cost that compounds every few weeks. If the market is in backwardation — near contracts more expensive than far ones — the fund benefits. Over years, these roll costs can meaningfully reduce returns versus the index itself.

Capital and what drives performance

GSG raises capital by issuing shares to investors who want commodity exposure, and those dollars flow directly into commodity futures. The fund has no revenue stream of its own — it is purely a pass-through vehicle. Whatever happens to commodity prices happens to the fund’s value. If oil rallies 20 percent, the futures holdings gain; if wheat falls, they lose. The fund charges an annual expense ratio to cover management and administrative costs.

What makes GSG different from owning commodities directly is that it offers instantaneous liquidity, transparent pricing on a stock exchange, and fractional ownership. You can buy one share instead of a contract for 1,000 barrels of oil. That accessibility is why millions of investment advisors and individuals use it. What you give up is the ability to take physical delivery and the higher precision of managing individual commodity positions.

The fund’s capital is entirely at the mercy of commodity cycles. When inflation fears peak and investors flee paper assets for tangible goods, inflows surge and GSG’s assets grow. When deflation concerns set in or investors rotate to stocks and bonds, inflows dry up and the fund shrinks. Over longer periods, the fund’s performance has tracked the fortunes of global growth and energy demand, with a notable spike during the 2022 energy crisis and periodic dips during recessions.

How to research it

GSG’s prospectus (filed with the SEC under its CIK 0001332174) lists the index methodology and current holdings. The annual report itemizes expenses and performance versus the S&P GSCI benchmark. The fund’s website publishes daily fact sheets showing the weighting of each commodity group and the composition of current positions. For anyone considering commodity exposure, the comparison between GSG, competitors like DBC (which uses a different weighting), and the underlying index itself reveals the cost of index tracking and the impact of contango or backwardation on real returns. Most financial platforms also publish GSG’s historical price alongside the spot prices of oil and other major commodities, showing how closely the fund tracks.