The New York Custom House Found A Lack Of Complete Records For 1920 Through June 1930. Source: U.S. Statistics Bureau, Bureau Of Foreign And Domestic Commerce, Monthly Summary Of Commerce And Finance - Monthly Summary Of Foreign Commerce, Etc.
This NBER data series m05023 appears on the NBER website in Chapter 5 at http://www.nber.org/databases/macrohistory/contents/chapter05.html.
NBER Indicator: m05023
Release: NBER Macrohistory Database
National Bureau of Economic Research, Lead Stocks, Banded Customs In Warehouse for United States [M05023USM601NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M05023USM601NNBR/, November 28, 2015.