The law of general average is a legal principle of maritime law according to which all parties in a sea venture proportionally share any losses resulting from a voluntary sacrifice of part of the ship or cargo to save the whole in an emergency.
In the exigencies of hazards faced at sea, crew members often have precious little time in which to determine precisely whose cargo they are jettisoning. Thus, to avoid quarrelling that could waste valuable time, there arose the equitable practice whereby all the merchants whose cargo landed safely would be called on to contribute a portion, based upon a share or percentage, to the merchant or merchants whose goods had been tossed overboard to avert imminent peril.
While general average traces its origins in ancient maritime law, still it remains part of the admiralty law of most countries.
The first codification of general average was the York Antwerp Rules of 1890. American companies accepted it in 1949. General average requires three elements which are clearly stated by Mr. Justice Grier in Barnard v. Adams:
"1st. A common danger: a danger in which vessel, cargo and crew all participate; a danger imminent and apparently 'inevitable,' except by voluntarily incurring the loss of a portion of the whole to save the remainder."
"2nd. There must be a voluntary jettison, jactus, or casting away, of some portion of the joint concern for the purpose of avoiding this imminent peril, periculi imminentis evitandi causa, or, in other words, a transfer of the peril from the whole to a particular portion of the whole."
"3rd. This attempt to avoid the imminent common peril must be successful".