Source: P.H. Douglas, Real Wages In The United States, 1890-1926, Pp. 239-240; The Movement Of Money And Real Earnings In The United States, 1926-1928, P. 10, (University Of Chicago Studies In Business Administration.)
This NBER data series m08040 appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: m08040
Release: NBER Macrohistory Database
National Bureau of Economic Research, Average Absolute Annual Earnings of Employees Or Wage Earners In All Manufacturing Industries for United States [M08040USM302NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M08040USM302NNBR, February 14, 2016.