NOTES: Shaded areas indicate U.S recessions, as defined by the National Bureau of Economic Research. Total finished goods. Converted to 1990 base year index by the Bureau of Transportation Statistics.
SOURCES: Air carrier, domestic, scheduled service (freight): U.S. Department of Transportation, Bureau of Transportation Statistics, TranStats Database, T-1, Schedule P-11, and Schedule P-12 data, available at http://www.transtats.bts.gov/ as of Sep. 1, 2015, special tabulation. Truck: 1990-2003: Eno Transportation Foundation, Inc., Transportation in America (Washington, DC: 2007), p. 46. 2004-07: U.S. Department of Commerce, U.S. Census Bureau, 2009 Transportation Annual Survey (Washington, DC: January 2011), table 2.1, available at http://www.census.gov/services/ as of Aug. 9, 2011, special tabulation. Class I rail: Association of American Railroads, Railroad Facts (Washington, DC: Annual Issues), p. 34 and similar pages in previous editions. Producer Price Index: U.S. Department of Labor, Bureau of Labor Statistics, Producer Price Index-Commodities (finished goods), available at http:// www.bls.gov/ppi/ as of Sept. 1, 2015.