TECHNICAL NOTE                                                

Import and Export Merchandise and Services Price Indexes - All indexes use a modified Laspeyres 
formula and are not seasonally adjusted. Price indexes are reweighted annually, with a 2-year lag in the 
weights. Published series use a base year of 2000=100 where possible. More detailed index series and 
additional information may be obtained at www.bls.gov/mxp or by calling (202) 691-7101.

Merchandise Goods Classification Systems - The merchandise price indexes are published using three 
classification systems. Items are classified by end use according to the Bureau of Economic Analysis 
Classification System, by industry according to the North American Industry Classification System 
(NAICS), and by product category according to the Harmonized System (HS). While classification by 
end use and product category are self-explanatory, some notes are in order for classifying items by 
industry. In the NAICS imports and exports tables, items are classified by output industry, not input 
industry. As an example, NAICS import index 326 (plastics and rubber products manufacturing) 
includes outputs such as manufactured plastic rather than inputs such as petroleum. The NAICS 
classification structure also matches the classification system used by the Producer Price Index (PPI) to 
produce the NAICS primary products indexes.

Import Price Indexes - 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.  

Export Price Indexes - Products have been classified by the Harmonized Schedule B classification 
system of the U.S. Bureau of the Census. The prices used are generally either "free alongside ship" 
(f.a.s.) factory or "free on board" (f.o.b.) transaction prices, depending on the practices of the individual 
industry. Prices used in the grain index, excluding rice, are obtained from the U.S. Department of 
Agriculture.

Services Price Indexes - Indexes for import and export air passenger fares calculate changes in the 
average revenue received per passenger by foreign carriers from U.S. residents and by U.S. carriers from 
foreign residents, respectively. Data are obtained from an airline consulting service and report on tickets 
sold by travel agencies, travel websites, and directly by the airlines. Taxes and fees are included in both 
the import and export air passenger fares indexes. Import air passenger fares data have used the airline 
consulting service source since September 2008. Before April 2018, the export air passenger fares data 
were collected directly by BLS from U.S. airlines. The air freight indexes are calculated from data 
collected directly from airlines. These data exclude mail and passenger baggage. The scope of the 
service being priced is the movement of freight from airport to airport only, and does not include any 
ground transportation or port service. The air freight indexes are presented using two definitions: 
balance of payments (which represents transactions between U.S. and foreign residents) and 
international (which represents transactions inbound to and outbound from the United States.) Fact 
sheets specifying detailed information for each services industry are available at www.bls.gov/mxp 
under "MXP Publications."

Import Indexes by Locality of Origin - Prices used in these indexes are a subset of the data collected 
for the import price indexes. Beginning with January 2002, the indexes are defined by locality of origin 
using a nomenclature based upon the North American Industry Classification System (NAICS). 
Nonmanufactured goods are defined as NAICS 11 and 21, and manufactured goods are defined as 
NAICS 31-33. 

Relative Importance - A relative importance is a specific index's price-updated value share (expressed 
as a percentage) of overall imports or exports at a specific point in time. Relative importance values are 
affected by the trade weights at the point indexes are reweighted and index changes relative to other 
indexes since the reweight point. If an index is rising in value relative to other indexes over time, the 
relative importance will increase as well. 
 
Revision Policy - To reflect the availability of late reports and corrections by respondents, monthly data 
may be revised in each of the 3 months after original publication. After 3 months, no further data 
revisions take place. For example, data first published in the January release will be subject to revision 
in the releases for February, March, and April.

Rounding Policy - Index values are rounded to the tenth decimal place after being calculated. All 
percent changes are then derived from the rounded index values and subsequently rounded to the tenth 
decimal place.

Uses of the Data - The primary use of the indexes is to deflate trade statistics, notably the foreign trade 
sector of the National Income and Product Accounts (NIPA) constructed by the Department of 
Commerce. Other published indexes are useful for general market analysis. For trade in international 
services, balance of payments indexes are used for deflating NIPA, while international indexes are more 
appropriate for market analysis. Merchandise and services indexes also can be used to study U.S. 
competitiveness and to compute price elasticities, and the merchandise import indexes by country or 
region of origin are useful in terms of trade analysis.

Email Subscription - The U.S. import and export price indexes news release is available through an 
email subscription service at www.bls.gov/bls/list.htm. 
 
Additional Information - More detailed data are available on the Import/Export Price Indexes home 
page at www.bls.gov/mxp. For import and export price indexes data requests, send an email to 
mxpinfo@bls.gov.   
Information from this release will be made available to sensory impaired individuals upon request.  
Voice phone: (202)-691-5200; Federal Relay Service: 1-(800)-877-8339.