U.S. Census Bureau, A Profile of U.S. Importing and Exporting Companies, 2012-2013
U.S Census Bureau, 2013 County Business Patterns (CBP).
Current Population Survey (CPS). 2013 Annual Social and Economic Supplement
2013 Annual Survey of Manufactures (ASM).
A Profile of U.S. Importing and Exporting Companies, 2012-2013 For more information on the data used in the Profile of U.S. Importing and Exporting Companies and accuracy of the data see https://www.census.gov/foreign-trade/guide/sec2.html#source