The Data For 1936-1940 Were Computed By NBER From Data In Statistics Of Income (See Notes); 1938 Was Adjusted By NBER To Conform To 1937 Industrial Classification (See Notes). The Data For 1939-1940 Are Based On 1938 Standard Industrial Classification. Source: Bureau Of Internal Revenue: Statistics Of Income, 1916 And Successive Years.
This NBER data series a09019 appears on the NBER website in Chapter 9 at http://www.nber.org/databases/macrohistory/contents/chapter09.html.
NBER Indicator: a09019
Release: NBER Macrohistory Database
National Bureau of Economic Research, Deficits, Transportation and Other Public Utility Companies for United States [A09019USA144NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/A09019USA144NNBR/, August 3, 2015.