"The dominance of Southern California as the Asia gateway is facing a lot more competition," said maritime consultant John Martin, who analyzed the trade data.

The loss in market share represented an estimated 12,300 direct and indirect California jobs in 2013, and more than $112m in state and local tax revenue, according to Martin's research.

The sudden growth of ship size has ports across the world scrambling to update infrastructure. Many are moving faster than L.A. and Long Beach, which are in the throes of multibillion-dollar expansions.

Ports along the East Coast and in Houston have invested billions of dollars to deepen harbors, expand terminals and upgrade rail systems that connect to lucrative markets in the Midwest. The port of Savannah, Ga., has more than doubled the volume of imported container goods over the last decade, while the Canadian government and railways expanded British Columbia's Port of Prince Rupert to become a direct competitor to U.S. ports farther south.

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