Data From July 1930-1932 Were Computed By NBER From The Source. Source: Computed By The National Industrial Conference Board From Data In Icc "Wage Statistics."
This NBER data series q08035 appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: q08035
Release: NBER Macrohistory Database
National Bureau of Economic Research, Average Hours of Work Per Week, Class I Railroad Employees, Skilled and Semi-Skilled Shop Workers for United States [Q08035USQ065NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/Q08035USQ065NNBR, February 12, 2016.