Series Excludes Switching And Terminal Companies Throughout; Series 01251 Includes Switching And Terminal Companies From February 1937 On. Data For 1921-January 1935 Are Based On Daily Averages. Data For February 1935-August 1943 Are Based On First Of The Month (The Published End-Of-Month Figures Being Placed Forward One Month) Centered By A Two Month Moving Average. For 1920, No Serviceable Freight Locomotive Data Were Available For The New York Central Railroad. Source: Data Computed By NBER From Series 03003 (Revenue Ton-Miles) And Series 01251 (Serviceable Freight Locomotives); Both Series Are Based On Interstate Commerce Commission Sources.
This NBER data series m03055 appears on the NBER website in Chapter 3 at http://www.nber.org/databases/macrohistory/contents/chapter03.html.
NBER Indicator: m03055
Release: NBER Macrohistory Database
National Bureau of Economic Research, Revenue Ton-Miles Per Serviceable Freight Locomotive, Class I Railroads for United States [M03055USM594NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M03055USM594NNBR/, July 5, 2015.