Products have been classified by the Harmonized Tariff Schedule of the United States Annotated (TSUSA). Import prices are based on U.S. dollar prices paid by the U.S. importer. The prices are generally either "free on board" (f.o.b.) foreign port or "cost, insurance, and freight" (c.i.f.) U.S. port transaction prices, depending on the practices of the individual industry. The index for crude petroleum is calculated from data collected by the U.S. Department of Energy.