During Processing It Was Discovered That Monthly And Quarterly Figures For 1931 As Provided By NBER Do Not Agree, But Data Have Not Been Changed. The Annual Figure Provided Here Was Computed From Monthly Data. Source: Computed By NBER By Dividing Series (Net Ton-Miles) By Series (Aggregate Coal Consumption By Freight Steam Locomotive).
This NBER data series m03083 appears on the NBER website in Chapter 3 at http://www.nber.org/databases/macrohistory/contents/chapter03.html.
NBER Indicator: m03083
Release: NBER Macrohistory Database
National Bureau of Economic Research, Net Ton-Miles Per Pound of Fuel Consumed By Steam Locomotives In Freight Service for Great Britain [M03083GBM465NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M03083GBM465NNBR/, October 13, 2015.