Maritime transport is the key to international trading since it allows to move large quantity of goods at a considerably reduced cost. This is one of the reasons why it concentrates around 80% of International Trade.
The main International maritime routes are connecting Asia-America, Asia-Europe, Europe-America. They form a transversal line which crosses the globe passing by the Suez Channel and Panama Channel.
Spain is located in a privileged position, between Asia and America. Many of the merchandises coming from Asia tranship at spanish ports before connecting to North or South America. Also, the cargo coming from America to Mediterranean countries tranships on spanish ports. This is the reason for shipping lines such as MAERSK or MSC to use Algeciras or Valencia as hub ports.