Source: Rorty, Harvard Business Review, January, 1923, P. 159, For 1877-1898; For 1899 And Following Years, See "Industrial Activity As Related To Long Term Growth Percentage Deviations, " American Telephone And Telegraph Company.
This NBER data series m12002a appears on the NBER website in Chapter 12 at http://www.nber.org/databases/macrohistory/contents/chapter12.html.
NBER Indicator: m12002a
Release: NBER Macrohistory Database
National Bureau of Economic Research, Index of Industrial Activity for United States [M1202AUSM510NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M1202AUSM510NNBR/, October 9, 2015.