The TSAs measure the magnitude of in-house transportation services by estimating the inputs used by each industry for its in-house transportation activities. To do this, the TSAs rearrange the I-O accounts using data on transportation from other sources. The following describes the steps involved. The major data sources are identified in table 10.
Transportation inputs include both intermediate inputs (e.g., motor vehicle gasoline) and value-added inputs (e.g., employee compensation, indirect business tax and nontax liability, and consumption of fixed capital). The value of these inputs for each industry in the U.S. I-O accounts' use table combines that for transportation and nontransportation purposes. The TSAs separate the value from transportation uses from all other uses through the following steps:
Technical documentation containing details on the above steps is available on request: at https://ntl.custhelp.com/app/ask
In the above steps, the TSAs assume the following:
The second step in the TSAs involves the production of the make and use tables. As noted earlier, the TSAs' make and use tables are I-O make and use tables modified to show estimates of transportation related inputs. First, estimates of transportation inputs for each industry are arranged in a matrix so that the rows and columns correspond to those in the intermediate industry portion of the I-O use table.19 Second, the estimates in the transportation input matrix are subtracted from the corresponding elements of the I-O use table, resulting in a residual use table that shows the intermediate and value-added inputs used by industries for nontransportation activities. Third, the TSAs use table is derived by combining the residual use table, an in-house transportation column vector for each in-house mode with the row sums from the transportation matrix, an in-house transportation row vector for each in-house mode with column totals from the transportation input matrix, and the final-demand portion of the I-O use table. Finally, the TSAs make table is formed by adding an additional column and an additional row for each in-house mode to the I-O make table. The values for this column and row are derived from row and column totals respectively from the transportation related input matrix.
The steps in measuring in-house transportation services in the 1997 TSAs follow, in general, those used in the 1992 and 1996 TSAs. However, the 1997 TSAs exclude some of the TRIs used in the 1992 and 1996 TSAs and use a slightly different technique for estimating other inputs used to provide transportation services. Additionally, the 1997 TSAs measure in-house transportation services for four modes (air, rail, truck, and water) and provide separate estimates for each. The 1992 and 1996 TSAs measured in-house transportation services for only two modes (bus and truck operations) and combined the two into a single measure.
The 1997 TSAs also differ significantly from the 1992 and 1996 TSAs because of a change in the industry classification system used in the I-O accounts. Prior to 1997, the I-O accounts were based on the Standard Industrial Classification System (SIC) and since 1997, have been based on the North American Industry Classification System (NAICS). NAICS differs from its predecessor SIC in that it:
The changes introduced by NAICS have resulted in most industries in the 1997 benchmark I-O accounts not being comparable to those in prior I-O accounts and, hence, in most industries in the 1997 TSAs not being comparable to those in prior TSAs.
To enable comparisons between the 1997 TSAs and 1992 TSAs, this report presents revised numbers for the 1992 TSAs using the 1997 TSAs procedure at the sector level. The 1996 TSAs were not re-estimated using the 1997 TSAs procedure due to a lack of sufficient detail in the inputs.
18 Adjustments were made after applying the for-hire relationship to ensure that the value of the transportation and nontransportation component of each commodity used by an industry equals that in the I-O use table.
19 Inputs for for-hire transportation industries in this matrix are all zero because these industries, by assumption, do not have any in-house transportation activities.
20 For information on the treatment of secondary products in the 1997 U.S. I-O accounts, see: Ann M. Lawson et al., "Benchmark Input-Output Accounts of the United States, 1997," Survey of Current Business, 2002, 82(12), p. 2, available at http://www.bea.gov/scb/pdf/2002/12December/1202I-OAccounts2.pdf as of Mar. 15, 2011.