Number of Digits
The longer the string of digits, the greater the degree of specificity of the commodity. One or two digit strings represent greatly aggregated data for broad categories of commodities. Seven or ten digit strings represent fairly specific commodities.
Systems in Use
The two main systems in use today for international trade statistics are the Harmonised System (HS) and the Standard International Trade Classification (SITC). Before the United States adopted HS in 1989, some of its published data was organized according to the Tariff Schedules of the United States of America (TSUSA), and really early data may just be organized under verbal headings..
Be aware of the revision being used for the data that you're studying and use the appropriate revision to look up the code.
Indexes and Keyword Searching
Although you can get a code number quickly from a keyword search or from an alphabetic index in the printed code books, the full definitions will give you a better idea about how that commodity is being defined and show its context to other commodities.
In electronic sources, you can generally search for matching text to find commodities or else drill down by expanding a numerical hierarchy. Printed guides will have tables of contents for browsing or indexes for word lookup.
The latest version of the Harmonized System (HS) adopted by the United States is published by the U.S. International Trade Commission (ITC) as the Harmonized Tariff Schedule of the United States. Goes to the 10-digit level of detail.
Published by the United Nations as the Commodity Indexes for the Standard International Trade Classification. Usually not quite as detailed as the Harmonised System. Goes to the 5-digit level; some data sources are more detailed.
Paper (in Perkins/Bostock Library)
General printed sources to help get an idea of total trade flows between countries or commodity flows into or out of a single country, but not commodities from one specific country to another specific country.
Direction of Trade Statistics. Yearbook and Direction of Trade Statistics Quarterly
From the International Monetary Fund (IMF); available through the IMF eLibrary as PDF documents.
Data also available through a custom extraction tool at the IMF Data site.
Also in paper: Most recent Yearbook at Perkins/Bostock Ref. Desk HF1016 .D574 For paper or microfiche Quarterlies, see catalog.
FAO Statistical Yearbook.
From the Food and Agriculture Organisation. Includes trade movements of agricultural commodities.
Includes contents of the former FAO Yearbook.Trade, which is also available in paper. Paper goes back to 1958 under various titles at HD9000.4 .T7. The Yearbook of Food and Agricultural Statistics includes both trade and production statistics before then, back to 1947 at HD1421 .Y4 (at LSC).
International Trade Statistics Yearbook. Perkins/Bostock Ref. U.N. ST/ESA/ STAT/ SER.G/
From the United Nations.
Latest edition in Reference UN (Perkins Reference, 1st Floor), older at LSC.
WTO Annual Report.
From the World Trade Organisation. See Library Catalog for older editions.