Bulk carrier is a large single-deck ship which carries unpackaged cargo. The cargo is simply poured, tipped or pumped into the holds or tanks of the ship. Although there have been colliers for centuries carrying bulk coal, the modern concept of bulk cargo being loaded and discharged quickly into single-deck dry cargo ships from modern terminals equipped for handling bulk cargoes dates only from about 1957. Like container ships they were born of economic necessity. Tramp freight rates were very depressed in 1957, so a cheaper means of carrying bulk cargoes had to be found. In 1969–70 they proved to be one of the most lucrative ships to operate and have been one of the largest-growing types of ship outside the tanker fleets. Liberia and Panama are the main countries of registry. In 1962 there were only 21 bulk carriers over 40K DWT and the world total was only 611. During the last few years, iron ore, coal and grain have accounted for some 65% of seaborne dry bulk cargo movements. Other important bulk cargoes include bauxite, sugar, wood, wood pulp, wood chips, fertilisers and cars. Full cargoes such as cars and packaged lumber are sometimes referred to as ‘neo-bulks’.