The container entries data from U.S. Customs and Border Protection (CBP) represented in this section and the next and in figure 15 and figure 16 are different from the TEU data presented earlier in the report. The CBP entries data count individual container units, while the TEU data refer to 20-foot equivalent units (that is, one 20-foot container equals one TEU, and one 40-foot container equals two TEUs). Because containers come in different lengths (for example, 20 feet, 40 feet, and 48 feet), the CBP figures on individual units differ from the TEU figures, which convert the tonnage of goods moved in the containers into TEUs.
The challenge of handling large volumes of containerized imports from U.S. trading partners can also be seen in the number of individual container entries processed by CBP. After a slight decline in the number of oceanborne containers entering the United States in the aftermath of the September 11, 2001, attacks, the nation's seaports again began handling an increasing number of container units. In 2007, there were about 12 million oceanborne container entries into the United States, down slightly from 2006 but still double those of 2000 (figure 15). Maritime container entries peak in the summer months, when imported merchandise trade is delivered for the fall and holiday seasons (figure 16).