Series Is Presented Here As Two Variables--(1)--Original Data, 1907-1925 (2)--Original Data, 1920-1956. Source: Data Were Computed By NBER By Dividing Series 03016B (Freight Operating Revenues, Class I, Including Switching And Terminal Companies) By Series 03001 (Revenue And Non-Revenue Ton-Miles, Class I, Excluding Switching And Terminal Companies); Both Series Are From Interstate Commerce Commission Sources. Data For 1907-1919: "Operating Revenues And Expenses Of Large Steam Roads"; "Operating Revenues And Operating Expenses Of Class I Railways; Also From The U.S. Department Of Commerce, Survey Of Current Business, Issue Of December 1923, And 1932 Annual Supplement. Data For 1920 1925: Icc, "Revenue Traffic Statistics Of Class I Steam Railways In The United States."
This NBER data series m03003ab appears on the NBER website in Chapter 3 at http://www.nber.org/databases/macrohistory/contents/chapter03.html.
NBER Indicator: m03003ab
Release: NBER Macrohistory Database
National Bureau of Economic Research, Revenue Per Freight Ton-Mile, Class I Railroads for United States [M033ABUSM270NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M033ABUSM270NNBR/, December 1, 2015.