The World Shipping Council (WSC) undertook a survey of its members to obtain a more accurate estimate of the number of containers lost overboard on an annual basis.
The WSC’s members represent over 90 percent of the global containership capacity. Members were asked to provide the actual number of containers lost overboard for three previous consecutive years. Those carriers that responded represent over 70 percent of the global container ship capacity.
WSC assumed for the purpose of this analysis that the container losses for the 30% of the industry that did not respond to the survey would be roughly the same as the 70% of the industry that responded.
As a result, the total annual figure reported has been adjusted upward to provide an estimated loss figure for all carriers, both WSC members and non-members, and arrive at a total industry figure.
Based on the survey results, the WSC estimates that on average there are approximately 350 containers lost at sea each year,
not counting catastrophic events. When one counts the catastrophic losses, an average total loss per year of approximately 675 containers was observed. Catastrophic losses are rare. The number of containers lost in a catastrophic event can vary greatly - from 50 to several hundred.
Total industry losses obviously vary from year to year, but these numbers are well below the 2,000 to 10,000 per year that regularly appear publicly, and represent a very small fraction of container loads shipped each year.
More info here
http://www.worldshipping.org/industry-issues/safety/containers
