Data Include Switching And Terminal Companies Until 1933. Source: Computed By NBER From Series (Overtime Hours Paid For All Employees On Hourly Basis) And Series (Total Number Of Employees On Hourly Basis).
This NBER data series m08156 appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: m08156
Release: NBER Macrohistory Database
National Bureau of Economic Research, Overtime Hours Worked Per Month, Per Employee, All Employees On Hourly Basis, Class I Railroads for United States [M08156USM065NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M08156USM065NNBR, February 8, 2016.