And its system of locks restricts the Panama canal to vessels of a given beam, known in shipping as Panamax.

ECONOMIST: The Panama canal

The three bulk carriers are the first new shipbuilding order placed by ADM designed to accommodate new post-Panamax needs.

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The declines have been seen across all ship classes, with the Cape, Panamax and Supramax indices all touching new lows in the past week.

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Some think that the trend towards post-Panamax ships may slow down.

ECONOMIST: The Panama canal