The ratio between value of exports and volume of seaborne trade remained constant until
the first oil shock in 1973, underlining little changes in the composition of maritime shipping.
The first two significant changes in this ratio correspond to the first and second oil shocks,
implying that higher oil prices directly impacted the global value of exports. Afterwards, the
steady growth of the ratio is mainly attributed to the growth in the containerized trade of high
value merchandise, particularly at the beginning of the 21st century