Series Is Preseted Here As Two Variables--(1)--Original Data, 1907-1917, (2)--Original Data, 1915-1944. The Railroads Included In These Data Are The Same Throughout, Except That The Actual Number Of Roads Decreased Due To Consolidations, From About 175 To 118. The Figures Throughout, However, Are Comparable. Data Are The Average Of Bi-Weekly Statistics. Source: American Railway Association, "Unfilled Car Requisitions", Bulletin No. 6, August 17, 1917; Quarterly Journal Of Economics, Vol. 33, P. 179.
This NBER data series m03009a appears on the NBER website in Chapter 3 at http://www.nber.org/databases/macrohistory/contents/chapter03.html.
NBER Indicator: m03009a
Release: NBER Macrohistory Database
National Bureau of Economic Research, Freight Car Surplus for United States [M0309AUSM543NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M0309AUSM543NNBR, February 6, 2016.