Source: Ilse Mintz, "Deterioration In The Quality Of Foreign Bonds Issued In The United States, 1920-1930" (NBER)
This NBER data series q10068 appears on the NBER website in Chapter 10 at http://www.nber.org/databases/macrohistory/contents/chapter10.html.
NBER Indicator: q10068
Release: NBER Macrohistory Database
National Bureau of Economic Research, Default Index of Foreign Government Bonds Publicly Offered In United States for United States [Q10068USQ156NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/Q10068USQ156NNBR/, August 4, 2015.