Trade Tables: The source of the trade data in this publication is the U.S. Department of Commerce's Bureau of the Census. Once the trade data becomes available from the Bureau of the Census, 6-7 weeks after the trade has actually occurred, it is organized by the U.S. Department of Agriculture's Foreign Agricultural Service into commodity aggregations and tables that are useful to U.S. trade interests. The process of collecting, reporting, and publishing data typically takes 3 months. These data count all sea, air, and land shipments departing from or arriving at all U.S. customs districts. The units used to describe quantity vary according to product (e.g. metric tons for meat products, head or number for live animals, and dozen for eggs), and all meat products are quantified on a product-weight basis. Totals may not add due to rounding.

Export data are based on shippers' export declarations, which the Bureau of the Census requires at the time of shipment. Export values are reported in f.a.s. (free alongside ship) value at the U.S. point of departure, and are based on the transaction price, including inland freight, insurance, and other charges incurred in placing the product alongside the carrier at the U.S. point of export. The value excludes all costs beyond the point of export. The data may not always reflect the value as defined above, since exporters sometimes find it difficult to assign values in accordance with this definition.

Two points regarding U.S. export data are worth noting. First, since products are sometimes transshipped to other destinations, over- and under- counting of exports to their final destination is a problem. The country of final destination is defined as the country where the product is consumed or further processed, as known to the shipper at the time of export. Problems arise when shippers do not know the country of final destination, or the final destination is changed at a later date. Hong Kong, Singapore, and the Netherlands are three countries which typically transship many products, and are therefore assigned overstated U.S. export values. To a lesser extent (since the effect is more disbursed), some countries of East and Southeast Asia and the European Community may be assigned understated U.S. export values.

Second, under the terms of a 1987 agreement, the U.S. Bureau of the Census will report U.S. exports to Canada based on Canadian import data, and Statistics Canada will report Canadian exports to the United States based on U.S. Bureau of the Census import data. This agreement to change reporting methods came after both countries acknowledged that their export data significantly under-reported actual trade levels.

Import values are reported in "customs" value, defined as the price actually paid for the shipment at the point of origin when sold for export to the United States. It excludes all import duties, freight or insurance costs incurred in bringing the product to a U.S. point of entry.

Commodity Codes: In 1978, 1980, 1983, and January 1995 some commodity specifications and tariff codes were changed, resulting in shifts in the way individual commodities were categorized and aggregated. In recent years, the most comprehensive change to the U.S. commodity coding system came when the Harmonized Tariff Schedule was adopted beginning in 1989. Both export and import harmonized schedules use a ten-digit coding system (the earlier one was based on seven digits), and products are often broken down into greater detail (especially the import schedule) than was the case earlier.

The index on export and import commodity aggregations in this publication lists all the aggregations of individual commodities used in the tables. Both pre-harmonized 1988 codes and their corresponding harmonized 1989 codes are listed. Revisions in the commodity coding system result in the merging of some individual commodities while in other cases some groups become disaggregated. While this publication attempts to build commodity aggregations that are meaningful to agricultural trade specialists and maintain groupings that are as consistent as possible over time, some discrepancies are inevitable.

The complete list of traded commodities, their description, and associated codes are described in two separate publications. Exported commodities are described in the "Statistical Classifications of Domestic and Foreign Commodities Exported from the United States, Schedule B", published by the U.S. Department of Commerce, Bureau of the Census in Washington, DC. Imported commodities are described in the "Harmonized Tariff Schedule of the United States", published by the U.S. International Trade Commission in Washington, DC. Both publications are available from the U.S. Government Printing Office, Washington, DC 20402.

For information on the classification of individual commodities, please call the Trade Data Section, Bureau of the Census, U.S. Department of Commerce, Washington, DC at (301) 457-2242. For information on the commodity aggregations used in this publication, please call the Dairy, Livestock and Poultry Division, Foreign Agricultural Service, U.S. Department of Agriculture, Washington, DC at (202) 720-8031.

Some of the abbreviations commonly used in the Bureau of the Census commodity descriptions are as follows: CH (chilled ); ETC (et cetera); FR (fresh); FZ (frozen); N/ (not);NEC (not elsewhere classified); NOV (not over); N/OVER (not over); NSPF (not specifically provided for); OT (other); OV (over); Q (quota); W/ (with); W/O (without); X/ (excluding).