Extra Digits In The Data Are From NBER Worksheets. The Average For 1919-1928=1530.0; For 1929-1938=-563.7; For 1919-1938=483.1. Source: Simon Kuznets, "National Income And Its Composition, 1919-1938, " P. 276
This NBER data series a10055 appears on the NBER website in Chapter 10 at http://www.nber.org/databases/macrohistory/contents/chapter10.html.
NBER Indicator: a10055
Release: NBER Macrohistory Database
National Bureau of Economic Research, Savings of Entrepreneurs for United States [A10055USA144NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/A10055USA144NNBR, February 8, 2016.