Refined products concentrate in a small number of trading and storage hubs, and stocks at those hubs are watched as a proxy for regional product balance. The three that matter most are Amsterdam-Rotterdam-Antwerp in northwest Europe, Singapore for Asia, and Fujairah in the Middle East Gulf.

These hubs exist where storage, refining, blending and shipping all coincide. That combination is what makes them price-setting: a cargo can arrive, be stored, be blended to a different specification, and be re-exported, which means the hub does not merely hold product but transforms it. Blending capability is why hub stocks respond to arbitrage economics rather than only to local demand.

Hub stock data has a different character from national inventory statistics. It is usually compiled by a commercial provider or an industry association from the tank operators themselves, published weekly, and covers independent storage only, which excludes refinery-owned tankage. So a hub number is a partial measure of a partial region, and its usefulness comes from consistency over time rather than from completeness.

The interpretation runs through the arbitrage. A hub builds stock when product arrives faster than it leaves, and both sides of that are arbitrage-driven: cargoes come when the landed economics work, and leave when another region pays more. So hub stocks are a read on relative regional value, which is a different and more specific claim than a read on global product supply.