Effective demand

Effective demand for sea transport is the volume of cargo actually moved, measured in tonne-miles: tonnes of cargo multiplied by the distance carried. It captures both how much is shipped and how far, so a long-haul trade adds more demand than a short one for the same tonnage. Tonne-mile demand is the standard denominator in shipping market analysis because vessel supply is fixed in deadweight while utilization depends on voyage distance. Trade pattern shifts, such as longer voyages around the Cape after canal disruption, raise effective demand without any rise in cargo volume.