These Data Are Also Adjusted For Long-Term Trend. Source: The Annalist, January 16, 1931, P. 162 For Data Through 1918; Thereafter Data Furnished By The E.W. Axe Company.
This NBER data series m12005a appears on the NBER website in Chapter 12 at http://www.nber.org/databases/macrohistory/contents/chapter12.html.
NBER Indicator: m12005a
Release: NBER Macrohistory Database
National Bureau of Economic Research, Index of Trade and Industrial Activity for United States [M1205AUSM156SNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M1205AUSM156SNBR/, August 4, 2015.