Source: Harry Jerome, Migration And Business Cycles, National Bureau Of Economic Research, Publication 9, P.248.
This NBER data series m08005 appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: m08005
Release: NBER Macrohistory Database
National Bureau of Economic Research, Index of Factory Employment for United States [M08005USM325NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M08005USM325NNBR, February 6, 2016.