Source: National Industrial Conference Board; 1925-1931 Data Are From Wages, Hours, And Employment In The United States, 1914-1936, Nicb Studies No. 229, 1936; 1932-1933 Data Are From A Supplement To The Nicb Service Letter, June 1938; 1934-1935 Data Are From The Nicb Economic Record, March 28, 1940; 1936-1942 Data Are From The Nicb Management Record, February 1945.
This NBER data series m08229 appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: m08229
Release: NBER Macrohistory Database
National Bureau of Economic Research, Index of Factory Payrolls, Heavy Equipment for United States [M08229USM330NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M08229USM330NNBR, February 11, 2016.