The increased use of oceanborne containers in transporting U.S. international trade continues to affect port operations and the distribution of total maritime trade among U.S. ports. Before the mid-1980s, when U.S. trade with Pacific Rim Asian countries was modest, east coast ports handled the majority of U.S. international maritime trade. As trade with Asia grew, the east coast ports' share of the value of trade declined and west coast ports' share increased (figure 10). Eventually, west coast ports surpassed east coast ports in maritime cargo handled, and this trend has continued to today. Also during this period, changes in industrial activity in the Midwest affected the volume and type of cargo moving through Great Lakes ports. For example, the relocation of final automobile assembly plants and companies that produce auto parts had an impact on manufacturing activities in the Midwest. With the emergence of automakers and parts producers in other parts of the United States, maritime cargo originating in the Midwest and cargo transport via the Great Lakes dwindled. Gulf of Mexico ports experienced a modest increase in their relative share as trade with Latin America grew.
Over half of U.S. containerized merchandise trade, measured in terms of TEUs, passes through west coast ports. In 2007, 55 percent of the containerized imports and exports passed through these ports, up from 42 percent in 1980 (figure 10). West coast ports as a region grew the fastest during this period (figure 11).
Although west coast ports handled the most container trade, they also had a larger share of the oceanborne containerized trade deficit, in terms of export-import balance, than other regional ports. Today, west coast ports serve more as import gateways to the United States than as export gateways to the rest of the world. In contrast, east coast ports handle more exports than imports, despite the decline in their regional market share.
Container trade also affects the pattern of freight movement within the United States. Nearly all U.S. oceanborne container trade is transported throughout the country by either rail carriers, long-haul truck carriers, or local truck carriers. Some ports use short-sea shipping as an alternative to transport goods shorter distances.9 The availability and efficiency of intermodal transportation in moving these goods to and from any U.S. port increases shippers' choices of transportation modes and port facilities, allowing ports to effectively use their economies of scale to attract cargo from beyond their immediate region. The growth in U.S. containerized cargo shipping is placing pressure on the nation's transportation network and affects local traffic congestion and delays in the urban areas surrounding the major U.S. container ports. (See Spotlight 1 on landside access to the seaports.)
9 Short-sea shipping describes the movement of freight along coastal waterways (for example, from Long Beach to Portland or from New York/New Jersey to Savannah). It includes the movement of containers and wet and dry bulk cargoes.