Twenty-foot Equivalent Unit

A twenty-foot equivalent unit (TEU) is the volume of one twenty-foot shipping container. It is also a unit of measurement that has, against all odds, become poetry.

The world's container fleet is described in TEU. The capacity of a port, the size of a ship, the throughput of a canal -- all in this stubborn little unit. There is something Borgesian about it: a measurement built around an object that no longer dominates the trade. Modern ships carry twenty-thousand TEU; almost all of them are forty-foot boxes. The twenty-foot box is everywhere, and almost nowhere.

To use the unit honestly is to remember it. The TEU is a metaphor for how supply chains keep their old vocabulary even as the world they describe transforms beneath the words.

• First definedcirca 1968, MARAD
• In useuniversally, all carriers
• See alsoFEU · HCU · reefer slot

The Bullwhip Effect

A small wobble at the consumer end of a supply chain becomes a large wobble at the producer end -- the way a flick at the handle of a bullwhip becomes a crack at the tip.

Consider toilet paper. The consumer buys two extra rolls, "just in case." The shop notices a 12% bump in weekly demand and doubles its order. The distributor, seeing a surge, triples its order. The factory, watching its order book swell, spins up a fourth shift. By the time the signal reaches the pulp mill, the original wobble of one extra roll has become an order for an additional thousand metric tonnes of softwood pulp.

Then the consumer, having stockpiled, stops buying for two weeks. The signal travels back up the chain: shops pause orders, distributors halt, factories idle the fourth shift, the pulp mill -- which has just felled the trees -- has nowhere to send them.

The bullwhip is not a malfunction. It is what a chain made of independent decision-makers does when it is asked to be a single nervous system. The cure, when there is one, is shared visibility -- which is to say, it is communication, which is to say, it is trust.