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5. Data Sources and Methodology

Key data used for our work are obtained from the U.S. Department of Commerce, the Bureau of Economic Analysis (BEA), and the U.S. Census Bureau (Census). None of these data sources, however, is readily usable for our purposes. Therefore, to produce tables presented in this report, we needed to fill in the gaps of these data sources. Our work is mainly based on BEA data, but we use data from the Census as a cross-reference. Appendix A contains a detailed list of the data sources used for our work. Following is a description of data sources and procedures used to produce tables presented in this report.

5.1 Government Investment in Transportation

Gross government capital investment in transportation is classified as investment in infrastructure and in rolling stock. The consensus is that equipment used for providing and maintaining the transportation infrastructure may be seen as a component of infrastructure despite the fact that the government sector must have made and will still make capital investment in transportation equipment other than rolling stock (e.g., computers for operating transportation facilities from highways to airports). It should be noted that there is no identifiable source of data that can be used for a reliable estimate of government investment in transportation equipment that is not blended with infrastructure. Therefore, we do not specify government investment in transportation equipment other than rolling stocks. The available data from the Census also show that government investment in transportation equipment is insignificant compared with government investment in construction, land, and existing structures, all of which are components of infrastructure.

Government investment in transportation infrastructure is grouped by transportation mode, such as highways, air, water, and transit, including railroad. Data on government investment in "highways and streets" are adopted from BEA, Fixed Assets Table 7.5. Data on government investment in other transportation infrastructures are obtained from BEA, the Government Division. The government annual purchase of motor vehicles, including automobiles, trucks and buses, is estimated from BEA, National Accounts, Table for Auto Output (i.e., underlying table 8.8U). More specifically, government purchase of motor vehicles (excluding employee reimbursement and government investment in motor vehicles for defense) is counted as government capital outlays on rolling stock for the highway and mass transit modes. At the current stage, there are no data available on government purchases of non-defense rolling stock for other transportation modes.

5.2. Business Investment in Transportation

Estimates for business investment in transportation are developed based on BEA data on capital investment by industry and by asset type, 1901-2000. Our report groups industries into two sectors for the purposes of measuring investment, the transportation industry, and all others, which we refer to as non-transportation industries. Six modes are specified within the transportation industry. They are: highways, air, water, mass transit, railroad, and pipelines. For the transportation sector, the following three types of assets are specified: infrastructure, rolling stock, and other. Non-transportation industries include agricultural, mining and construction, manufacturing, communications, utilities, trade, finance, insurance and real estate, and service industries. For non-transportation industries, only investment in rolling stock (including motor vehicles, aircrafts, ships and boats, and railroad equipment) is identified as transportation investment.

5.3. Households Purchase of Rolling Stock

Household purchase of rolling stock is classified into three modes: highways and streets (road), air, and water. For road transportation, household purchase of rolling stock includes automobiles, motorcycles, and bicycles. Household purchase of aircraft and boats are classified as air transportation and water transportation, respectively. As shown in Appendix A, all these data are obtained through personal communication with BEA and from various BEA web links.

Our communication with the BEA staff also indicated that government purchases for other type of rolling stocks such as airplanes and ships including investment in ship construction are exclusively for defense purposes, which is beyond our scope of work.