Data Layout for concordance_8901.asc
column 1    	-  10 digit Harmonized Tariff System (HTS) number, leading zeros suppressed
column 2   	-  4 digit SIC code (1987 revision), leading zeros suppressed

Data Layout for multilateral_8901.asc
column 1   	-  Year
column 2   	-  4 digit SIC code (1987 revision), leading zeros suppressed
column 3   	-  Value of exports (dollars)
column 4  	-  Customs Value, General Imports (dollars)
column 5   	-  Customs Value, Imports for Consumption (dollars)
column 6 	-  Dutiable Value (dollars)
column 7 	-  Calculated Duties (dollars)
column 8 	-  Import Charges (dollars)

Data Layout for bilateral_8901_19xx.asc
column 1   	-  UN Country Code (see COUNTRY.TXT at http://www.internationaldata.org/data/usixd/imports/country.txt)
column 2   	-  Year
column 3   	-  4 digit SIC code (1987 revision), leading zeros suppressed
column 4   	-  Value of exports (dollars)
column 5  	-  Customs Value, General Imports (dollars)
column 6   	-  Customs Value, Imports for Consumption (dollars)
column 7 	-  Dutiable Value (dollars)
column 8 	-  Calculated Duties (dollars)
column 9 	-  Import Charges (dollars)

Definitions (see "US Imports, Exports and Tariff Data, 1989-2001" (NBER 9387))
1.  The export value is the selling price or cost if not sold, including inland  freight, insurance, and other charges to the U.S. port of export, but excluding unconditional discounts and commissions.  This value is called the F.a.s. (free alongside ship) value.   
2. Customs Import Value.  The Customs value reflects the value of imports as appraised by the U.S. Customs Service.  This value is generally defined as the price actually paid or payable for merchandise when sold for exportation to the United States, excluding U.S. import duties, freight, insurance and other charges incurred in bringing the merchandise to the United States. 
3.  Imports for Consumption.  Imports for Consumption measure the total of  merchandise that has physically cleared through Customs either entering  consumption channels immediately or entering after withdrawal for consumption  from bonded warehouses under Customs custody or from Foreign Trade Zones. Many countries use the term "special imports" to designate statistics  compiled on this basis.  
4.  General Imports.  General Imports measure the total physical arrivals  of merchandise from foreign countries, whether such merchandise enters consumption channels immediately or is entered into bonded warehouses or Foreign Trade Zones under Customs custody.  
5. Dutiable Value of Imports and Calculated Duty.  The dutiable value represents in general, the Customs value of foreign merchandise imported into the United States which is subject to duty.  The calculated duty represents the estimated duty collected.  Estimated data are calculated by the Census based on the applicable rate(s) of duty as shown in the HTS.       
6.  Import Charges.  The import charges represent the aggregate cost of all freight, insurance and other charges (excluding import duties) incurred in bringing the merchandise from alongside the carrier at the port of exportation and placing it alongside the carrier at the first port of entry in the United States.   The sum of the Customs value and the charges is the c.i.f. (cost, insurance and freight) value.