What makes something a commodity?

A commodity is a good the market treats as interchangeable: buyers accept one producer's units as equivalent to another's, so the decision comes down to price. That is the test, and it is about the market rather than the material itself. Sugar passes it, because white sugar of a stated specification is the same product whoever refined it, so there is a market of interchangeable units and a published price to track. A fragrance or a specific surfactant blend for a shampoo does not pass it. It is made to one supplier's own recipe and cannot be swapped for a competitor's version without changing your product, so there is no single market price for it. It is an ingredient in your recipe, not a commodity, even though you buy it by the kilo.

Why that distinction decides whether a price series can exist:

• A commodity has a standard behind it. On a commodity exchange it is the standard stated in the contract that defines the commodity, not any quality belonging to one producer's material. That shared standard is what makes one price series meaningful for every buyer.
• Being a raw material is not the test. Mass-produced unspecialized goods such as chemicals and computer memory are traded as commodities because they are interchangeable, while a branded item with its own design and perceived quality is not, however basic it looks.
• It is a spectrum, not a yes or no. Even electricity is differentiated where buyers can pay more for renewable generation. If your specification requires a certification, a recycled content or one approved supplier, a market price is a reference for the underlying material rather than your own buying price.
• Search the material by name in the 'Add resources' pop-up using 'Search by keyword'. If you find it there, it is tracked as a commodity and you can put its price series on the chart.
• If you do not find it, look one step up its production chain and track that instead: a polymer part traces back to crude oil, a steel bracket to iron ore, paper to softwood. An ingredient that is not itself a commodity is usually made from ones that are.

For an overview of what is available to track, please see 'Where can I find the commodities?'