Source: National Industrial Conference Board, For 1925-1931 Data: Wages, Hours, And Employment In The United States, Nicb Studies No. 229, 1936; For 1932-1933 Data: Supplement To Nicb Service Letter, June 1938; For 1934-1935: Nicb Economic Record, March 28, 1940; For 1936-1942: Nicb Management Record, January 1945.
This NBER data series m08224 appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: m08224
Release: NBER Macrohistory Database
National Bureau of Economic Research, Index of Factory Employment, Machine and Machine Tools for United States [M08224USM330NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M08224USM330NNBR/, September 3, 2015.