TECHNICAL NOTE Import and Export Goods 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 Goods Indexes - Items are 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 Goods Indexes - Items are 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 Price Indexes by Locality of Origin - Prices used in these indexes are a subset of the data collected for the import price indexes. The indexes are specific to a country, region, or grouping and, beginning with January 2002, are based on the North American Industry Classification System (NAICS) covering goods-producing industries. Nonmanufactured goods are defined as NAICS 11 and 21, and manufactured goods are defined as NAICS 31-33. Export Price Indexes by Locality of Destination - Prices used in these indexes are a subset of the data collected for the export price indexes. The indexes are specific to a country, region, or grouping and are based on the North American Industry Classification System (NAICS) covering goods-producing industries. Nonmanufactured goods are defined as NAICS 11 and 21, and manufactured goods are defined as NAICS 31-33. Terms of Trade Indexes - Terms of trade indexes measure the relative price of exports in terms of import prices for a specific country, region, or grouping. The indexes are calculated as one country, region, or grouping's all-export goods price index divided by the corresponding all-import goods price index on a scale of 100. 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. 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 firstname.lastname@example.org. 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.