Source: J. Shiskin Of NBER, Table 6, January 29, 1965
This NBER data series m16001 appears on the NBER website in Chapter 16 at http://www.nber.org/databases/macrohistory/contents/chapter16.html.
NBER Indicator: m16001
Release: NBER Macrohistory Database
National Bureau of Economic Research, Amplitude-Adjusted Composite Index of Twenty Leading Series, Unweighted for United States [M16001USM358SNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M16001USM358SNBR/, October 4, 2015.