Series Is Presented Here As Two Variables--(1)--Seasonally Adjusted Data, 1921-1939 (2)--Seasonally Adjusted Data, 1939-1968. Source: H. Barger, Outlay And Income In The United States, 1921-1938, Pp. 325 And Following; Data For 1939 Are From Dr. Barger'S Files
This NBER data series q05103a appears on the NBER website in Chapter 5 at http://www.nber.org/databases/macrohistory/contents/chapter05.html.
NBER Indicator: q05103a
Release: NBER Macrohistory Database
National Bureau of Economic Research, Gross Private Domestic Investment Change In Business Inventories, Current Dollars for United States [Q0503AUSQ244SNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/Q0503AUSQ244SNBR/, July 27, 2015.