Data frame giving the number of damage incidents and aggregate months of service by ship type, year of construction, and period of operation.
ships
type
type: "A"
to "E"
.
year
year of construction: 1960--64, 65--69, 70--74, 75--79
(coded as "60"
, "65"
, "70"
, "75"
).
period
period of operation : 1960--74, 75--79.
service
aggregate months of service.
incidents
number of damage incidents.