The movement of shipping containers from Asia to the U.S. returned to near-historic levels in 2014, supported by a recovery in the U.S. economy and greater consumer spending by the middle class.

In terms of 20-foot equivalent containers (TEUs), U.S. sea trade imports from Asia rose 6.8% from the 2013 level, to reach 14.23 million TEUs in 2014, according to Zepol, a U.S. company that tracks trade data. The 2014 total is just short of the record 14.24 million TEUs recorded in 2007.

Shipments from Asia to the U.S. rose steadily from the 1990s, but then plunged in 2008 and 2009 after fallout from the global financial crisis. In 2013, traffic in containers began to rebound, and improved further as consumer demand increased for a range of goods in 2014. Trade in auto parts and housing-related goods such as furniture and flooring materials was busy throughout the year, and shipments of toys and clothing picked up during the Christmas season.

Container imports from China, the leading exporter accounting for 60% of all goods shipped to the U.S., rose 6.9% in 2014, and shipments from second-ranking South Korea grew 3.2%.

Taiwan, which ranked fourth, shipped 11.7% more TEUs, and Singapore boosted its shipments by 17.4% to jump past Japan, where shipments rose 3.8% to 610,000 TEUs.

Even so, ports along the U.S. West Coast have been embroiled in labor disputes since May, and offloading of cargo has lagged to the point that some ports are chronically congested.

The result has led to uncertainty among exporters about shipping to West Coast ports, according to Japanese shipping company Nippon Yusen, and an upward effect on rates.

Wanting to avoid the congested West Coast, exporters show a growing demand to ship containers to the U.S. East Coast. The current shipping rate for 40-foot containers (FEUs) from Asia to the East Coast is now about $4,500 per FEU, up 40% from the same time last year. In comparison, the rate to West Coast ports hovers at $1,900 per FEU, up just 3% from last year.

Demand to move containers along other shipping routes is also on the rise. Container traffic from Asia to Europe totaled 12.9 million TEUs from January to October 2014, up 8.9% from the same 10 months of 2013, according to the Japan Maritime Center, which monitors sea trade.

And the movement of containers within Asia along the routes linking China, Japan and Southeast Asia rose 2.3% from January to October 2014.