|Mode||Value (percent)||Weight (percent)|
|NAFTA trade, totala||100.0||100.0|
|Other and unknown||5.4||0.2|
|U.S. NAFTA imports, total||100.0||100.0|
|Other and unknown||4.0||0.1|
|U.S. NAFTA exports, totala||100.0||100.0|
|Other and unknown||7.1||0.3|
a BTS estimated the export weight for truck, rail, pipeline, and other and unknown based on value-to-weight ratios from the import data. This was necessary, because export weights for surface modes are not currently reported. Weight for water and air exports and imports are from U.S. Department of Commerce, U.S. Census Bureau.
Note: Value based on millions of U.S. dollars; weight based on millions of short tons.
Sources: Compiled by USDOT, Bureau of Transportation Statistics (BTS), May 2002. Water and air data-U.S. Department of Commerce, U.S. Census Bureau, Foreign Trade Division, U.S. Exports of Merchandise, CD-ROM and U.S. Imports of Merchandise, CD-ROM, December 2001. Total, truck, rail, pipeline, other and unknown data-USDOT, BTS, Transborder Surface Freight Data 2002; and special calculation, May 2002.