Measure convoy success by cargo delivered

Convoys increase the chance that cargo arrives on a usable timetable, not merely that hulls survive. Threat reports can leave ships waiting in port or divert them until food and other perishables spoil. Moisture can make rice expand enough to damage its ship, while wet grain can create other dangerous conditions. Grouping merchants raises the level of enemy risk they can tolerate because they offer mutual support and share a defensive cordon. Convoy success should therefore be measured in usable cargo delivered as well as ships sunk.