The Data Were Obtained From Unemployment Figures Subtracted From 100%. Source: Reichsarbeitsblatt 1914 And Following Issues; For 1923-30, See Jahrbuch Deutschen Baugemeinsbund.
This NBER data series m08022 appears on the NBER website in Chapter 8 at http://www.nber.org/databases/macrohistory/contents/chapter08.html.
NBER Indicator: m08022
Release: NBER Macrohistory Database
National Bureau of Economic Research, Employment, Building Trades for Germany [M08022DEM514NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M08022DEM514NNBR/, November 26, 2015.