Source: US. Bureau of Economic Analysis
Release: Gross Domestic Product
A Guide to the National Income and Product Accounts of the United States (NIPA) - (http://www.bea.gov/national/pdf/nipaguid.pdf)
Exports (from table 1.1, line 16) plus receipts of factor income (From table 1.9, line 2)
US. Bureau of Economic Analysis, Exports of Goods and Services, GNP-Basis (DISCONTINUED) [EXPGSN], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/EXPGSN, August 31, 2016.