The largest cargo vessel ever to call at an American port will dock in Los Angeles Saturday. The CMA CGM Benjamin Franklin, owned by a Marseilles-based shipping company, can hold the equivalent of 18,000 shipping containers, each 20 feet long. It’ll travel back and forth from China to America’s west coast ports. It’s part of a new wave of mega ships that are the bobbing, floating embodiment of economies of scale.

“They’re about three and a half football fields long,” said Mark Szakonyi, with the Journal of Commerce, part of IHS Maritime. “This all started before the recession hit. The container lines were seeing the price of bunker fuel go up and realizing that they could gain much larger greater economies of scale by building larger more fuel efficient vessels.”

By carrying larger loads, companies can lower their operating costs. However, the shipping industry is now facing an excess of capacity amid weakening demand.

Investments in larger ships have also spurred investments in ports, to be able to handle the increased size of ships and their loads.

“We’ve dredged for deeper water, we’ve fortified the wharves over the decades,” said Phillip Sanfield, a spokesperson for the Port of Los Angeles. “And it’s not getting a ship in here and having it fit in, it’s processing the ship quickly.”

The bigger the ship, the longer it takes to load and unload.