Data For January 1920 Were Not Available For Series 01250. Source: Computed By NBER By Dividing Seasonal Values Of Series 03003 Revenue Ton-Miles) By Seasonal Values Of Series 01250 (Total Locomotives Assigned To Freight Service).
This NBER data series m03066 appears on the NBER website in Chapter 3 at http://www.nber.org/databases/macrohistory/contents/chapter03.html.
NBER Indicator: m03066
Release: NBER Macrohistory Database
National Bureau of Economic Research, Revenue Ton-Miles Per Locomotive Assigned To Freight Service for United States [M03066USM604SNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M03066USM604SNBR, February 8, 2016.