Deadweight

Deadweight is a term used in physics, engineering, and related fields to describe a static load that does not vary over time. It refers to the portion of a system’s weight that must be supported regardless of how the system is used. The weight of a body is W = m g, where m is mass and g is the acceleration due to gravity. In structures, dead loads include the weight of fixed components such as beams, floors, walls, roofs, and fixed equipment, which remain constant, in contrast to live loads that vary with occupancy and use.

In maritime contexts, deadweight tonnage (DWT) measures a ship’s carrying capacity. It equals the difference between the vessel’s loaded displacement and its light displacement, representing the maximum weight of cargo, fuel, stores, crew, and provisions the ship can safely carry. DWT excludes the ship’s own weight, which is accounted for by the light displacement, and increases as the ship is loaded.

In economics, deadweight loss refers to the reduction in total surplus that results from market inefficiencies. It occurs when interventions such as taxes, subsidies, price controls, or monopoly pricing prevent trades that would maximize welfare, or cause trades that reduce welfare to occur. The concept is commonly illustrated by analyzing the areas of lost efficiency on supply-and-demand diagrams.