aThe Bureau of Transportation Statistics estimated weight of exports for truck, rail, pipeline, mail and other and unknown modes based on the import weight- to-value ratios that vary by country, mode, and commodity. bWeight data for water transportation vary from those officially reported by the U.S. Army Corps of Engineers because the data in this figure exclude intransit shipments.
Notes: U.S. North American Free Trade Agreement (NAFTA) refers to U.S. trade with Canada and Mexico. “Other” includes shipments transported by mail, other, and unknown modes, and shipments through Foreign Trade Zones.
Sources: Truck, Rail, Pipeline, Other—U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, Transborder Freight Data,available at http://www.bts.gov/programs/ international/transborder/ accessed August 2012. Water, Air—U.S. Depart- ment of Commerce, Census Bureau, Foreign Trade Division, FT920 U.S. Merchandise Trade: Selected Highlights accessed August 2012.